add a new Attestation token, for proving claims or DID ownership

Specification is TBD

.github/workflows/bench.yml

@@ -0,0 +1,34 @@
+name: go continuous benchmark
+on:
+  push:
+    branches:
+      - main
+
+permissions:
+  contents: write
+  deployments: write
+
+jobs:
+  benchmark:
+    name: Run Go continuous benchmark
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version: "stable"
+      - name: Run benchmark
+        run: go test -v ./... -bench=. -run=xxx -benchmem | tee output.txt
+
+      - name: Store benchmark result
+        uses: benchmark-action/github-action-benchmark@v1
+        with:
+          name: Go Benchmark
+          tool: 'go'
+          output-file-path: output.txt
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          # Push and deploy GitHub pages branch automatically
+          auto-push: true
+          # Show alert with commit comment on detecting possible performance regression
+          alert-threshold: '200%'
+          comment-on-alert: true

.github/workflows/gotest.yml

@@ -7,14 +7,14 @@ jobs:
       fail-fast: false
       matrix:
         os: [ "ubuntu" ]
-        go: [ "1.21.x", "1.22.x", "1.23.x", ]
+        go: [ "1.22.x", "1.23.x", ]
     env:
       COVERAGES: ""
     runs-on: ${{ matrix.os }}-latest
     name: ${{ matrix.os}} (go ${{ matrix.go }})
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
-      - uses: actions/setup-go@v2
+      - uses: actions/setup-go@v5
         with:
           go-version: ${{ matrix.go }}
       - name: Go information
@@ -22,6 +22,6 @@ jobs:
           go version
           go env
       - name: Run tests
-        run: go test -v ./...
+        run: go test -v ./... -tags jwx_es256k
       - name: Check formatted
         run: gofmt -l .

LICENSE.md

@@ -29,7 +29,7 @@ Verbatim copies of both licenses are included below:
 ```
                                  Apache License
                            Version 2.0, January 2004
-                        http://www.apache.org/licenses/
+                        https://www.apache.org/licenses/
 
    TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
 

Readme.md

@@ -0,0 +1,76 @@
+<div align="center">
+  <a href="https://github.com/ucan-wg/go-ucan" target="_blank">
+    <img src="https://raw.githubusercontent.com/ucan-wg/go-ucan/v1/assets/logo.png" alt="go-ucan Logo" height="250"></img>
+  </a>
+
+  <h1 align="center">go-ucan</h1>
+
+  <p>
+    <img src="https://img.shields.io/badge/UCAN-v1.0.0--rc.1-blue" alt="UCAN v1.0.0-rc.1">
+    <a href="https://github.com/ucan-wg/go-ucan/tags">
+        <img alt="GitHub Tag" src="https://img.shields.io/github/v/tag/ucan-wg/go-ucan">
+    </a>
+    <a href="https://github.com/ucan-wg/go-ucan/actions?query=">
+      <img src="https://github.com/ucan-wg/go-ucan/actions/workflows/gotest.yml/badge.svg" alt="Build Status">
+    </a>
+    <a href="https://ucan-wg.github.io/go-ucan/dev/bench/">
+        <img alt="Go benchmarks" src="https://img.shields.io/badge/Benchmarks-go-blue">
+    </a>
+    <a href="https://github.com/ucan-wg/go-ucan/blob/v1/LICENSE.md">
+        <img alt="Apache 2.0 OR MIT License" src="https://img.shields.io/badge/License-Apache--2.0_OR_MIT-green">
+    </a>
+    <a href="https://pkg.go.dev/github.com/ucan-wg/go-ucan">
+      <img src="https://img.shields.io/badge/Docs-godoc-blue" alt="Docs">
+    </a>
+    <a href="https://discord.gg/JSyFG6XgVM">
+      <img src="https://img.shields.io/static/v1?label=Discord&message=join%20us!&color=mediumslateblue" alt="Discord">
+    </a>
+  </p>
+</div>
+
+This is a go library to help the next generation of web and decentralized applications make use
+of UCANs in their authorization flows.
+
+User Controlled Authorization Networks (UCANs) are a way of doing authorization where users are fully in control. OAuth is designed for a centralized world, UCAN is the distributed user controlled version.
+
+## Resources
+
+### Specifications
+
+The UCAN specification is separated in multiple sub-spec:
+- [Main specification](https://github.com/ucan-wg/spec)
+- [Delegation](https://github.com/ucan-wg/delegation/tree/v1_ipld)
+- [Invocation](https://github.com/ucan-wg/invocation)
+- [Container](https://github.com/ucan-wg/container)
+
+Not implemented yet:
+- [Revocation](https://github.com/ucan-wg/revocation/tree/first-draft)
+- [Promise](https://github.com/ucan-wg/promise/tree/v1-rc1)
+
+### Talks
+
+- [Decentralizing Auth, and UCAN Too - Brooklyn Zelenka (2023)](https://www.youtube.com/watch?v=MuHfrqw9gQA)
+- [What's New in UCAN 1.0 - Brooklyn Zelenka (2024)](https://www.youtube.com/watch?v=-uohQzZcwF4)
+
+## Status
+
+`go-ucan` currently support the required parts of the UCAN specification: the main specification, delegation and invocation. It leverages the sibling project [`go-did-it`](https://github.com/MetaMask/go-did-it) for easy and extensible DID support.
+
+Besides that, `go-ucan` also includes:
+- support for encrypted values in token's metadata
+
+## Getting Help
+
+For usage questions, usecases, or issues reach out to us in our `go-ucan`
+[Discord channel](https://discord.gg/3EHEQ6M8BC).
+
+We would be happy to try to answer your question or try opening a new issue on
+Github.
+
+## UCAN Gopher
+
+Artwork by [Bruno Monts](https://www.instagram.com/bruno_monts). Thank you [Renee French](http://reneefrench.blogspot.com/) for creating the [Go Gopher](https://blog.golang.org/gopher)
+
+## License
+
+This project is licensed under the dual license [Apache 2.0 OR MIT](https://github.com/ucan-wg/go-ucan/blob/v1/LICENSE.md).

capability/command/command.go

@@ -1,142 +0,0 @@
-package command
-
-import (
-	"errors"
-	"fmt"
-	"strings"
-)
-
-const (
-	separator = "/"
-)
-
-// ErrNew indicates that the wrapped error was encountered while creating
-// a new Command.
-var ErrNew = errors.New("failed to create Command from elems")
-
-// ErrParse indicates that the wrapped error was encountered while
-// attempting to parse a string as a Command.
-var ErrParse = errors.New("failed to parse Command")
-
-// ErrorJoin indicates that the wrapped error was encountered while
-// attempting to join a new segment to a Command.
-var ErrJoin = errors.New("failed to join segments to Command")
-
-// ErrRequiresLeadingSlash is returned when a parsing a string that
-// doesn't start with a [leading slash character].
-//
-// [leading slash character]: https://github.com/ucan-wg/spec#segment-structure
-var ErrRequiresLeadingSlash = parseError("a command requires a leading slash character")
-
-// ErrDisallowsTrailingSlash is returned when parsing a string that [ends
-// with a trailing slash character].
-//
-// [ends with a trailing slash character]: https://github.com/ucan-wg/spec#segment-structure
-var ErrDisallowsTrailingSlash = parseError("a command must not include a trailing slash")
-
-// ErrUCANNamespaceReserved is returned to indicate that a Command's
-// first segment would contain the [reserved "ucan" namespace].
-//
-// [reserved "ucan" namespace]: https://github.com/ucan-wg/spec#ucan-namespace
-var ErrUCANNamespaceReserved = errors.New("the UCAN namespace is reserved")
-
-// ErrRequiresLowercase is returned if a Command contains, or would contain,
-// [uppercase unicode characters].
-//
-// [uppercase unicode characters]: https://github.com/ucan-wg/spec#segment-structure
-var ErrRequiresLowercase = parseError("UCAN path segments must must not contain upper-case characters")
-
-func parseError(msg string) error {
-	return fmt.Errorf("%w: %s", ErrParse, msg)
-}
-
-var _ fmt.Stringer = (*Command)(nil)
-
-// Command is a concrete messages (a "verb") that MUST be unambiguously
-// interpretable by the Subject of a UCAN.
-//
-// A [Command] is composed of a leading slash which is optionally followed
-// by one or more slash-separated Segments of lowercase characters.
-//
-// [Command]: https://github.com/ucan-wg/spec#command
-type Command struct {
-	segments []string
-}
-
-// New creates a validated command from the provided list of segment
-// strings.  An error is returned if an invalid Command would be
-// formed
-func New(segments ...string) (*Command, error) {
-	return newCommand(ErrNew, segments...)
-}
-
-func newCommand(err error, segments ...string) (*Command, error) {
-	if len(segments) > 0 && segments[0] == "ucan" {
-		return nil, fmt.Errorf("%w: %w", err, ErrUCANNamespaceReserved)
-	}
-
-	cmd := Command{segments}
-
-	return &cmd, nil
-}
-
-// Parse verifies that the provided string contains the required
-// [segment structure] and, if valid, returns the resulting
-// Command.
-//
-// [segment structure]: https://github.com/ucan-wg/spec#segment-structure
-func Parse(s string) (*Command, error) {
-	if !strings.HasPrefix(s, "/") {
-		return nil, ErrRequiresLeadingSlash
-	}
-
-	if len(s) > 1 && strings.HasSuffix(s, "/") {
-		return nil, ErrDisallowsTrailingSlash
-	}
-
-	if s != strings.ToLower(s) {
-		return nil, ErrRequiresLowercase
-	}
-
-	// The leading slash will result in the first element from strings.Split
-	// being an empty string which is removed as strings.Join will ignore it.
-	return newCommand(ErrParse, strings.Split(s, "/")[1:]...)
-}
-
-// [Top] is the most powerful capability.
-//
-// This function returns a Command that is a wildcard and therefore represents the
-// most powerful abilily.  As such it should be handle with care and used
-// sparingly.
-//
-// [Top]: https://github.com/ucan-wg/spec#-aka-top
-func Top() *Command {
-	cmd, _ := New()
-
-	return cmd
-}
-
-// IsValid returns true if the provided string is a valid UCAN command.
-func IsValid(s string) bool {
-	_, err := Parse(s)
-
-	return err == nil
-}
-
-// Join appends segments to the end of this command using the required
-// segment separator.
-func (c *Command) Join(segments ...string) (*Command, error) {
-	return newCommand(ErrJoin, append(c.segments, segments...)...)
-}
-
-// Segments returns the ordered segments that comprise the Command as a
-// slice of strings.
-func (c *Command) Segments() []string {
-	return c.segments
-}
-
-// String returns the composed representation the command.  This is also
-// the required wire representation (before IPLD encoding occurs.)
-func (c *Command) String() string {
-	return "/" + strings.Join([]string(c.segments), "/")
-}

capability/policy/literal/literal.go

@@ -1,52 +0,0 @@
-package literal
-
-import (
-	"github.com/ipld/go-ipld-prime"
-	"github.com/ipld/go-ipld-prime/node/basicnode"
-)
-
-func Node(n ipld.Node) ipld.Node {
-	return n
-}
-
-func Link(cid ipld.Link) ipld.Node {
-	nb := basicnode.Prototype.Link.NewBuilder()
-	nb.AssignLink(cid)
-	return nb.Build()
-}
-
-func Bool(val bool) ipld.Node {
-	nb := basicnode.Prototype.Bool.NewBuilder()
-	nb.AssignBool(val)
-	return nb.Build()
-}
-
-func Int(val int64) ipld.Node {
-	nb := basicnode.Prototype.Int.NewBuilder()
-	nb.AssignInt(val)
-	return nb.Build()
-}
-
-func Float(val float64) ipld.Node {
-	nb := basicnode.Prototype.Float.NewBuilder()
-	nb.AssignFloat(val)
-	return nb.Build()
-}
-
-func String(val string) ipld.Node {
-	nb := basicnode.Prototype.String.NewBuilder()
-	nb.AssignString(val)
-	return nb.Build()
-}
-
-func Bytes(val []byte) ipld.Node {
-	nb := basicnode.Prototype.Bytes.NewBuilder()
-	nb.AssignBytes(val)
-	return nb.Build()
-}
-
-func Null() ipld.Node {
-	nb := basicnode.Prototype.Any.NewBuilder()
-	nb.AssignNull()
-	return nb.Build()
-}

capability/policy/match.go

@@ -1,163 +0,0 @@
-package policy
-
-import (
-	"cmp"
-	"fmt"
-
-	"github.com/ipld/go-ipld-prime"
-	"github.com/ipld/go-ipld-prime/datamodel"
-	"github.com/ipld/go-ipld-prime/must"
-
-	"github.com/ucan-wg/go-ucan/v1/capability/policy/selector"
-)
-
-// Match determines if the IPLD node matches the policy document.
-func Match(policy Policy, node ipld.Node) bool {
-	for _, stmt := range policy {
-		ok := matchStatement(stmt, node)
-		if !ok {
-			return false
-		}
-	}
-	return true
-}
-
-func matchStatement(statement Statement, node ipld.Node) bool {
-	switch statement.Kind() {
-	case KindEqual:
-		if s, ok := statement.(equality); ok {
-			one, _, err := selector.Select(s.selector, node)
-			if err != nil || one == nil {
-				return false
-			}
-			return datamodel.DeepEqual(s.value, one)
-		}
-	case KindGreaterThan:
-		if s, ok := statement.(equality); ok {
-			one, _, err := selector.Select(s.selector, node)
-			if err != nil || one == nil {
-				return false
-			}
-			return isOrdered(s.value, one, gt)
-		}
-	case KindGreaterThanOrEqual:
-		if s, ok := statement.(equality); ok {
-			one, _, err := selector.Select(s.selector, node)
-			if err != nil || one == nil {
-				return false
-			}
-			return isOrdered(s.value, one, gte)
-		}
-	case KindLessThan:
-		if s, ok := statement.(equality); ok {
-			one, _, err := selector.Select(s.selector, node)
-			if err != nil || one == nil {
-				return false
-			}
-			return isOrdered(s.value, one, lt)
-		}
-	case KindLessThanOrEqual:
-		if s, ok := statement.(equality); ok {
-			one, _, err := selector.Select(s.selector, node)
-			if err != nil || one == nil {
-				return false
-			}
-			return isOrdered(s.value, one, lte)
-		}
-	case KindNot:
-		if s, ok := statement.(negation); ok {
-			return !matchStatement(s.statement, node)
-		}
-	case KindAnd:
-		if s, ok := statement.(connective); ok {
-			for _, cs := range s.statements {
-				r := matchStatement(cs, node)
-				if !r {
-					return false
-				}
-			}
-			return true
-		}
-	case KindOr:
-		if s, ok := statement.(connective); ok {
-			if len(s.statements) == 0 {
-				return true
-			}
-			for _, cs := range s.statements {
-				r := matchStatement(cs, node)
-				if r {
-					return true
-				}
-			}
-			return false
-		}
-	case KindLike:
-		if s, ok := statement.(wildcard); ok {
-			one, _, err := selector.Select(s.selector, node)
-			if err != nil || one == nil {
-				return false
-			}
-			v, err := one.AsString()
-			if err != nil {
-				return false
-			}
-			return s.glob.Match(v)
-		}
-	case KindAll:
-		if s, ok := statement.(quantifier); ok {
-			_, many, err := selector.Select(s.selector, node)
-			if err != nil || many == nil {
-				return false
-			}
-			for _, n := range many {
-				ok := Match(s.statements, n)
-				if !ok {
-					return false
-				}
-			}
-			return true
-		}
-	case KindAny:
-		if s, ok := statement.(quantifier); ok {
-			_, many, err := selector.Select(s.selector, node)
-			if err != nil || many == nil {
-				return false
-			}
-			for _, n := range many {
-				ok := Match(s.statements, n)
-				if ok {
-					return true
-				}
-			}
-			return false
-		}
-	}
-	panic(fmt.Errorf("unimplemented statement kind: %s", statement.Kind()))
-}
-
-func isOrdered(expected ipld.Node, actual ipld.Node, satisfies func(order int) bool) bool {
-	if expected.Kind() == ipld.Kind_Int && actual.Kind() == ipld.Kind_Int {
-		a := must.Int(actual)
-		b := must.Int(expected)
-		return satisfies(cmp.Compare(a, b))
-	}
-
-	if expected.Kind() == ipld.Kind_Float && actual.Kind() == ipld.Kind_Float {
-		a, err := actual.AsFloat()
-		if err != nil {
-			panic(fmt.Errorf("extracting node float: %w", err))
-		}
-		b, err := expected.AsFloat()
-		if err != nil {
-			panic(fmt.Errorf("extracting selector float: %w", err))
-		}
-		return satisfies(cmp.Compare(a, b))
-	}
-
-	return false
-}
-
-func gt(order int) bool  { return order == 1 }
-func gte(order int) bool { return order == 0 || order == 1 }
-func lt(order int) bool  { return order == -1 }
-func lte(order int) bool { return order == 0 || order == -1 }

capability/policy/match_test.go

@@ -1,420 +0,0 @@
-package policy
-
-import (
-	"fmt"
-	"testing"
-
-	"github.com/ipfs/go-cid"
-	"github.com/ipld/go-ipld-prime"
-	cidlink "github.com/ipld/go-ipld-prime/linking/cid"
-	"github.com/ipld/go-ipld-prime/node/basicnode"
-	"github.com/stretchr/testify/require"
-
-	"github.com/ucan-wg/go-ucan/v1/capability/policy/literal"
-	"github.com/ucan-wg/go-ucan/v1/capability/policy/selector"
-)
-
-func TestMatch(t *testing.T) {
-	t.Run("equality", func(t *testing.T) {
-		t.Run("string", func(t *testing.T) {
-			np := basicnode.Prototype.String
-			nb := np.NewBuilder()
-			nb.AssignString("test")
-			nd := nb.Build()
-
-			pol := Policy{Equal(selector.MustParse("."), literal.String("test"))}
-			ok := Match(pol, nd)
-			require.True(t, ok)
-
-			pol = Policy{Equal(selector.MustParse("."), literal.String("test2"))}
-			ok = Match(pol, nd)
-			require.False(t, ok)
-
-			pol = Policy{Equal(selector.MustParse("."), literal.Int(138))}
-			ok = Match(pol, nd)
-			require.False(t, ok)
-		})
-
-		t.Run("int", func(t *testing.T) {
-			np := basicnode.Prototype.Int
-			nb := np.NewBuilder()
-			nb.AssignInt(138)
-			nd := nb.Build()
-
-			pol := Policy{Equal(selector.MustParse("."), literal.Int(138))}
-			ok := Match(pol, nd)
-			require.True(t, ok)
-
-			pol = Policy{Equal(selector.MustParse("."), literal.Int(1138))}
-			ok = Match(pol, nd)
-			require.False(t, ok)
-
-			pol = Policy{Equal(selector.MustParse("."), literal.String("138"))}
-			ok = Match(pol, nd)
-			require.False(t, ok)
-		})
-
-		t.Run("float", func(t *testing.T) {
-			np := basicnode.Prototype.Float
-			nb := np.NewBuilder()
-			nb.AssignFloat(1.138)
-			nd := nb.Build()
-
-			pol := Policy{Equal(selector.MustParse("."), literal.Float(1.138))}
-			ok := Match(pol, nd)
-			require.True(t, ok)
-
-			pol = Policy{Equal(selector.MustParse("."), literal.Float(11.38))}
-			ok = Match(pol, nd)
-			require.False(t, ok)
-
-			pol = Policy{Equal(selector.MustParse("."), literal.String("138"))}
-			ok = Match(pol, nd)
-			require.False(t, ok)
-		})
-
-		t.Run("IPLD Link", func(t *testing.T) {
-			l0 := cidlink.Link{Cid: cid.MustParse("bafybeif4owy5gno5lwnixqm52rwqfodklf76hsetxdhffuxnplvijskzqq")}
-			l1 := cidlink.Link{Cid: cid.MustParse("bafkreifau35r7vi37tvbvfy3hdwvgb4tlflqf7zcdzeujqcjk3rsphiwte")}
-
-			np := basicnode.Prototype.Link
-			nb := np.NewBuilder()
-			nb.AssignLink(l0)
-			nd := nb.Build()
-
-			pol := Policy{Equal(selector.MustParse("."), literal.Link(l0))}
-			ok := Match(pol, nd)
-			require.True(t, ok)
-
-			pol = Policy{Equal(selector.MustParse("."), literal.Link(l1))}
-			ok = Match(pol, nd)
-			require.False(t, ok)
-
-			pol = Policy{Equal(selector.MustParse("."), literal.String("bafybeif4owy5gno5lwnixqm52rwqfodklf76hsetxdhffuxnplvijskzqq"))}
-			ok = Match(pol, nd)
-			require.False(t, ok)
-		})
-
-		t.Run("string in map", func(t *testing.T) {
-			np := basicnode.Prototype.Map
-			nb := np.NewBuilder()
-			ma, _ := nb.BeginMap(1)
-			ma.AssembleKey().AssignString("foo")
-			ma.AssembleValue().AssignString("bar")
-			ma.Finish()
-			nd := nb.Build()
-
-			pol := Policy{Equal(selector.MustParse(".foo"), literal.String("bar"))}
-			ok := Match(pol, nd)
-			require.True(t, ok)
-
-			pol = Policy{Equal(selector.MustParse(".[\"foo\"]"), literal.String("bar"))}
-			ok = Match(pol, nd)
-			require.True(t, ok)
-
-			pol = Policy{Equal(selector.MustParse(".foo"), literal.String("baz"))}
-			ok = Match(pol, nd)
-			require.False(t, ok)
-
-			pol = Policy{Equal(selector.MustParse(".foobar"), literal.String("bar"))}
-			ok = Match(pol, nd)
-			require.False(t, ok)
-		})
-
-		t.Run("string in list", func(t *testing.T) {
-			np := basicnode.Prototype.List
-			nb := np.NewBuilder()
-			la, _ := nb.BeginList(1)
-			la.AssembleValue().AssignString("foo")
-			la.Finish()
-			nd := nb.Build()
-
-			pol := Policy{Equal(selector.MustParse(".[0]"), literal.String("foo"))}
-			ok := Match(pol, nd)
-			require.True(t, ok)
-
-			pol = Policy{Equal(selector.MustParse(".[1]"), literal.String("foo"))}
-			ok = Match(pol, nd)
-			require.False(t, ok)
-		})
-	})
-
-	t.Run("inequality", func(t *testing.T) {
-		t.Run("gt int", func(t *testing.T) {
-			np := basicnode.Prototype.Int
-			nb := np.NewBuilder()
-			nb.AssignInt(138)
-			nd := nb.Build()
-
-			pol := Policy{GreaterThan(selector.MustParse("."), literal.Int(1))}
-			ok := Match(pol, nd)
-			require.True(t, ok)
-		})
-
-		t.Run("gte int", func(t *testing.T) {
-			np := basicnode.Prototype.Int
-			nb := np.NewBuilder()
-			nb.AssignInt(138)
-			nd := nb.Build()
-
-			pol := Policy{GreaterThanOrEqual(selector.MustParse("."), literal.Int(1))}
-			ok := Match(pol, nd)
-			require.True(t, ok)
-
-			pol = Policy{GreaterThanOrEqual(selector.MustParse("."), literal.Int(138))}
-			ok = Match(pol, nd)
-			require.True(t, ok)
-		})
-
-		t.Run("gt float", func(t *testing.T) {
-			np := basicnode.Prototype.Float
-			nb := np.NewBuilder()
-			nb.AssignFloat(1.38)
-			nd := nb.Build()
-
-			pol := Policy{GreaterThan(selector.MustParse("."), literal.Float(1))}
-			ok := Match(pol, nd)
-			require.True(t, ok)
-		})
-
-		t.Run("gte float", func(t *testing.T) {
-			np := basicnode.Prototype.Float
-			nb := np.NewBuilder()
-			nb.AssignFloat(1.38)
-			nd := nb.Build()
-
-			pol := Policy{GreaterThanOrEqual(selector.MustParse("."), literal.Float(1))}
-			ok := Match(pol, nd)
-			require.True(t, ok)
-
-			pol = Policy{GreaterThanOrEqual(selector.MustParse("."), literal.Float(1.38))}
-			ok = Match(pol, nd)
-			require.True(t, ok)
-		})
-
-		t.Run("lt int", func(t *testing.T) {
-			np := basicnode.Prototype.Int
-			nb := np.NewBuilder()
-			nb.AssignInt(138)
-			nd := nb.Build()
-
-			pol := Policy{LessThan(selector.MustParse("."), literal.Int(1138))}
-			ok := Match(pol, nd)
-			require.True(t, ok)
-		})
-
-		t.Run("lte int", func(t *testing.T) {
-			np := basicnode.Prototype.Int
-			nb := np.NewBuilder()
-			nb.AssignInt(138)
-			nd := nb.Build()
-
-			pol := Policy{LessThanOrEqual(selector.MustParse("."), literal.Int(1138))}
-			ok := Match(pol, nd)
-			require.True(t, ok)
-
-			pol = Policy{LessThanOrEqual(selector.MustParse("."), literal.Int(138))}
-			ok = Match(pol, nd)
-			require.True(t, ok)
-		})
-	})
-
-	t.Run("negation", func(t *testing.T) {
-		np := basicnode.Prototype.Bool
-		nb := np.NewBuilder()
-		nb.AssignBool(false)
-		nd := nb.Build()
-
-		pol := Policy{Not(Equal(selector.MustParse("."), literal.Bool(true)))}
-		ok := Match(pol, nd)
-		require.True(t, ok)
-
-		pol = Policy{Not(Equal(selector.MustParse("."), literal.Bool(false)))}
-		ok = Match(pol, nd)
-		require.False(t, ok)
-	})
-
-	t.Run("conjunction", func(t *testing.T) {
-		np := basicnode.Prototype.Int
-		nb := np.NewBuilder()
-		nb.AssignInt(138)
-		nd := nb.Build()
-
-		pol := Policy{
-			And(
-				GreaterThan(selector.MustParse("."), literal.Int(1)),
-				LessThan(selector.MustParse("."), literal.Int(1138)),
-			),
-		}
-		ok := Match(pol, nd)
-		require.True(t, ok)
-
-		pol = Policy{
-			And(
-				GreaterThan(selector.MustParse("."), literal.Int(1)),
-				Equal(selector.MustParse("."), literal.Int(1138)),
-			),
-		}
-		ok = Match(pol, nd)
-		require.False(t, ok)
-
-		pol = Policy{And()}
-		ok = Match(pol, nd)
-		require.True(t, ok)
-	})
-
-	t.Run("disjunction", func(t *testing.T) {
-		np := basicnode.Prototype.Int
-		nb := np.NewBuilder()
-		nb.AssignInt(138)
-		nd := nb.Build()
-
-		pol := Policy{
-			Or(
-				GreaterThan(selector.MustParse("."), literal.Int(138)),
-				LessThan(selector.MustParse("."), literal.Int(1138)),
-			),
-		}
-		ok := Match(pol, nd)
-		require.True(t, ok)
-
-		pol = Policy{
-			Or(
-				GreaterThan(selector.MustParse("."), literal.Int(138)),
-				Equal(selector.MustParse("."), literal.Int(1138)),
-			),
-		}
-		ok = Match(pol, nd)
-		require.False(t, ok)
-
-		pol = Policy{Or()}
-		ok = Match(pol, nd)
-		require.True(t, ok)
-	})
-
-	t.Run("wildcard", func(t *testing.T) {
-		pattern := `Alice\*, Bob*, Carol.`
-
-		for _, s := range []string{
-			"Alice*, Bob, Carol.",
-			"Alice*, Bob, Dan, Erin, Carol.",
-			"Alice*, Bob  , Carol.",
-			"Alice*, Bob*, Carol.",
-		} {
-			func(s string) {
-				t.Run(fmt.Sprintf("pass %s", s), func(t *testing.T) {
-					np := basicnode.Prototype.String
-					nb := np.NewBuilder()
-					nb.AssignString(s)
-					nd := nb.Build()
-
-					statement, err := Like(selector.MustParse("."), pattern)
-					require.NoError(t, err)
-
-					pol := Policy{statement}
-					ok := Match(pol, nd)
-					require.True(t, ok)
-				})
-			}(s)
-		}
-
-		for _, s := range []string{
-			"Alice*, Bob, Carol",
-			"Alice*, Bob*, Carol!",
-			"Alice Cooper, Bob, Carol.",
-			"Alice, Bob, Carol.",
-			" Alice*, Bob, Carol. ",
-		} {
-			func(s string) {
-				t.Run(fmt.Sprintf("fail %s", s), func(t *testing.T) {
-					np := basicnode.Prototype.String
-					nb := np.NewBuilder()
-					nb.AssignString(s)
-					nd := nb.Build()
-
-					statement, err := Like(selector.MustParse("."), pattern)
-					require.NoError(t, err)
-
-					pol := Policy{statement}
-					ok := Match(pol, nd)
-					require.False(t, ok)
-				})
-			}(s)
-		}
-	})
-
-	t.Run("quantification", func(t *testing.T) {
-		buildValueNode := func(v int64) ipld.Node {
-			np := basicnode.Prototype.Map
-			nb := np.NewBuilder()
-			ma, _ := nb.BeginMap(1)
-			ma.AssembleKey().AssignString("value")
-			ma.AssembleValue().AssignInt(v)
-			ma.Finish()
-			return nb.Build()
-		}
-
-		t.Run("all", func(t *testing.T) {
-			np := basicnode.Prototype.List
-			nb := np.NewBuilder()
-			la, _ := nb.BeginList(5)
-			la.AssembleValue().AssignNode(buildValueNode(5))
-			la.AssembleValue().AssignNode(buildValueNode(10))
-			la.AssembleValue().AssignNode(buildValueNode(20))
-			la.AssembleValue().AssignNode(buildValueNode(50))
-			la.AssembleValue().AssignNode(buildValueNode(100))
-			la.Finish()
-			nd := nb.Build()
-
-			pol := Policy{
-				All(
-					selector.MustParse(".[]"),
-					GreaterThan(selector.MustParse(".value"), literal.Int(2)),
-				),
-			}
-			ok := Match(pol, nd)
-			require.True(t, ok)
-
-			pol = Policy{
-				All(
-					selector.MustParse(".[]"),
-					GreaterThan(selector.MustParse(".value"), literal.Int(20)),
-				),
-			}
-			ok = Match(pol, nd)
-			require.False(t, ok)
-		})
-
-		t.Run("any", func(t *testing.T) {
-			np := basicnode.Prototype.List
-			nb := np.NewBuilder()
-			la, _ := nb.BeginList(5)
-			la.AssembleValue().AssignNode(buildValueNode(5))
-			la.AssembleValue().AssignNode(buildValueNode(10))
-			la.AssembleValue().AssignNode(buildValueNode(20))
-			la.AssembleValue().AssignNode(buildValueNode(50))
-			la.AssembleValue().AssignNode(buildValueNode(100))
-			la.Finish()
-			nd := nb.Build()
-
-			pol := Policy{
-				Any(
-					selector.MustParse(".[]"),
-					GreaterThan(selector.MustParse(".value"), literal.Int(10)),
-					LessThan(selector.MustParse(".value"), literal.Int(50)),
-				),
-			}
-			ok := Match(pol, nd)
-			require.True(t, ok)
-
-			pol = Policy{
-				Any(
-					selector.MustParse(".[]"),
-					GreaterThan(selector.MustParse(".value"), literal.Int(100)),
-				),
-			}
-			ok = Match(pol, nd)
-			require.False(t, ok)
-		})
-	})
-}

capability/policy/policy.go

@@ -1,125 +0,0 @@
-package policy
-
-// https://github.com/ucan-wg/delegation/blob/4094d5878b58f5d35055a3b93fccda0b8329ebae/README.md#policy
-
-import (
-	"github.com/gobwas/glob"
-	"github.com/ipld/go-ipld-prime"
-
-	"github.com/ucan-wg/go-ucan/v1/capability/policy/selector"
-)
-
-const (
-	KindEqual              = "=="   // implemented by equality
-	KindGreaterThan        = ">"    // implemented by equality
-	KindGreaterThanOrEqual = ">="   // implemented by equality
-	KindLessThan           = "<"    // implemented by equality
-	KindLessThanOrEqual    = "<="   // implemented by equality
-	KindNot                = "not"  // implemented by negation
-	KindAnd                = "and"  // implemented by connective
-	KindOr                 = "or"   // implemented by connective
-	KindLike               = "like" // implemented by wildcard
-	KindAll                = "all"  // implemented by quantifier
-	KindAny                = "any"  // implemented by quantifier
-)
-
-type Policy []Statement
-
-type Statement interface {
-	Kind() string
-}
-
-type equality struct {
-	kind     string
-	selector selector.Selector
-	value    ipld.Node
-}
-
-func (e equality) Kind() string {
-	return e.kind
-}
-
-func Equal(selector selector.Selector, value ipld.Node) Statement {
-	return equality{KindEqual, selector, value}
-}
-
-func GreaterThan(selector selector.Selector, value ipld.Node) Statement {
-	return equality{KindGreaterThan, selector, value}
-}
-
-func GreaterThanOrEqual(selector selector.Selector, value ipld.Node) Statement {
-	return equality{KindGreaterThanOrEqual, selector, value}
-}
-
-func LessThan(selector selector.Selector, value ipld.Node) Statement {
-	return equality{KindLessThan, selector, value}
-}
-
-func LessThanOrEqual(selector selector.Selector, value ipld.Node) Statement {
-	return equality{KindLessThanOrEqual, selector, value}
-}
-
-type negation struct {
-	statement Statement
-}
-
-func (n negation) Kind() string {
-	return KindNot
-}
-
-func Not(stmt Statement) Statement {
-	return negation{stmt}
-}
-
-type connective struct {
-	kind       string
-	statements []Statement
-}
-
-func (c connective) Kind() string {
-	return c.kind
-}
-
-func And(stmts ...Statement) Statement {
-	return connective{KindAnd, stmts}
-}
-
-func Or(stmts ...Statement) Statement {
-	return connective{KindOr, stmts}
-}
-
-type wildcard struct {
-	selector selector.Selector
-	pattern  string
-	glob     glob.Glob // not serialized
-}
-
-func (n wildcard) Kind() string {
-	return KindLike
-}
-
-func Like(selector selector.Selector, pattern string) (Statement, error) {
-	g, err := glob.Compile(pattern)
-	if err != nil {
-		return nil, err
-	}
-	return wildcard{selector, pattern, g}, nil
-}
-
-type quantifier struct {
-	kind       string
-	selector   selector.Selector
-	statements []Statement
-}
-
-func (n quantifier) Kind() string {
-	return n.kind
-}
-
-func All(selector selector.Selector, policy ...Statement) Statement {
-	return quantifier{KindAll, selector, policy}
-}
-
-func Any(selector selector.Selector, policy ...Statement) Statement {
-	return quantifier{KindAny, selector, policy}
-}

capability/policy/selector/parsing.go

@@ -1,160 +0,0 @@
-package selector
-
-import (
-	"fmt"
-	"strconv"
-	"strings"
-)
-
-func Parse(str string) (Selector, error) {
-	if len(str) == 0 {
-		return nil, newParseError("empty selector", str, 0, "")
-	}
-	if string(str[0]) != "." {
-		return nil, newParseError("selector must start with identity segment '.'", str, 0, string(str[0]))
-	}
-
-	col := 0
-	var sel Selector
-	for _, tok := range tokenize(str) {
-		seg := tok
-		opt := strings.HasSuffix(tok, "?")
-		if opt {
-			seg = tok[0 : len(tok)-1]
-		}
-		switch seg {
-		case ".":
-			if len(sel) > 0 && sel[len(sel)-1].Identity() {
-				return nil, newParseError("selector contains unsupported recursive descent segment: '..'", str, col, tok)
-			}
-			sel = append(sel, Identity)
-		case "[]":
-			sel = append(sel, segment{tok, false, opt, true, nil, "", 0})
-		default:
-			if strings.HasPrefix(seg, "[") && strings.HasSuffix(seg, "]") {
-				lookup := seg[1 : len(seg)-1]
-
-				if indexRegex.MatchString(lookup) { // index
-					idx, err := strconv.Atoi(lookup)
-					if err != nil {
-						return nil, newParseError("invalid index", str, col, tok)
-					}
-					sel = append(sel, segment{str: tok, optional: opt, index: idx})
-				} else if strings.HasPrefix(lookup, "\"") && strings.HasSuffix(lookup, "\"") { // explicit field
-					sel = append(sel, segment{str: tok, optional: opt, field: lookup[1 : len(lookup)-1]})
-				} else if sliceRegex.MatchString(lookup) { // slice [3:5] or [:5] or [3:]
-					var rng []int
-					splt := strings.Split(lookup, ":")
-					if splt[0] == "" {
-						rng = append(rng, 0)
-					} else {
-						i, err := strconv.Atoi(splt[0])
-						if err != nil {
-							return nil, newParseError("invalid slice index", str, col, tok)
-						}
-						rng = append(rng, i)
-					}
-					if splt[1] != "" {
-						i, err := strconv.Atoi(splt[1])
-						if err != nil {
-							return nil, newParseError("invalid slice index", str, col, tok)
-						}
-						rng = append(rng, i)
-					}
-					sel = append(sel, segment{str: tok, optional: opt, slice: rng})
-				} else {
-					return nil, newParseError(fmt.Sprintf("invalid segment: %s", seg), str, col, tok)
-				}
-			} else if fieldRegex.MatchString(seg) {
-				sel = append(sel, segment{str: tok, optional: opt, field: seg[1:]})
-			} else {
-				return nil, newParseError(fmt.Sprintf("invalid segment: %s", seg), str, col, tok)
-			}
-		}
-		col += len(tok)
-	}
-	return sel, nil
-}
-
-func MustParse(sel string) Selector {
-	s, err := Parse(sel)
-	if err != nil {
-		panic(err)
-	}
-	return s
-}
-
-func tokenize(str string) []string {
-	var toks []string
-	col := 0
-	ofs := 0
-	ctx := ""
-
-	for col < len(str) {
-		char := string(str[col])
-
-		if char == "\"" && string(str[col-1]) != "\\" {
-			col++
-			if ctx == "\"" {
-				ctx = ""
-			} else {
-				ctx = "\""
-			}
-			continue
-		}
-
-		if ctx == "\"" {
-			col++
-			continue
-		}
-
-		if char == "." || char == "[" {
-			if ofs < col {
-				toks = append(toks, str[ofs:col])
-			}
-			ofs = col
-		}
-		col++
-	}
-
-	if ofs < col && ctx != "\"" {
-		toks = append(toks, str[ofs:col])
-	}
-
-	return toks
-}
-
-type parseerr struct {
-	msg string
-	src string
-	col int
-	tok string
-}
-
-func (p parseerr) Name() string {
-	return "ParseError"
-}
-
-func (p parseerr) Message() string {
-	return p.msg
-}
-
-func (p parseerr) Column() int {
-	return p.col
-}
-
-func (p parseerr) Error() string {
-	return p.msg
-}
-
-func (p parseerr) Source() string {
-	return p.src
-}
-
-func (p parseerr) Token() string {
-	return p.tok
-}
-
-func newParseError(message string, source string, column int, token string) error {
-	return parseerr{message, source, column, token}
-}

capability/policy/selector/selector.go

@@ -1,253 +0,0 @@
-package selector
-
-import (
-	"fmt"
-	"regexp"
-	"strings"
-
-	"github.com/ipld/go-ipld-prime"
-	"github.com/ipld/go-ipld-prime/datamodel"
-	"github.com/ipld/go-ipld-prime/schema"
-)
-
-// Selector describes a UCAN policy selector, as specified here:
-// https://github.com/ucan-wg/delegation/blob/4094d5878b58f5d35055a3b93fccda0b8329ebae/README.md#selectors
-type Selector []segment
-
-func (s Selector) String() string {
-	var res strings.Builder
-	for _, seg := range s {
-		res.WriteString(seg.String())
-	}
-	return res.String()
-}
-
-var Identity = segment{".", true, false, false, nil, "", 0}
-
-var (
-	indexRegex = regexp.MustCompile(`^-?\d+$`)
-	sliceRegex = regexp.MustCompile(`^((\-?\d+:\-?\d*)|(\-?\d*:\-?\d+))$`)
-	fieldRegex = regexp.MustCompile(`^\.[a-zA-Z_]*?$`)
-)
-
-type segment struct {
-	str      string
-	identity bool
-	optional bool
-	iterator bool
-	slice    []int
-	field    string
-	index    int
-}
-
-// String returns the segment's string representation.
-func (s segment) String() string {
-	return s.str
-}
-
-// Identity flags that this selector is the identity selector.
-func (s segment) Identity() bool {
-	return s.identity
-}
-
-// Optional flags that this selector is optional.
-func (s segment) Optional() bool {
-	return s.optional
-}
-
-// Iterator flags that this selector is an iterator segment.
-func (s segment) Iterator() bool {
-	return s.iterator
-}
-
-// Slice flags that this segment targets a range of a slice.
-func (s segment) Slice() []int {
-	return s.slice
-}
-
-// Field is the name of a field in a struct/map.
-func (s segment) Field() string {
-	return s.field
-}
-
-// Index is an index of a slice.
-func (s segment) Index() int {
-	return s.index
-}
-
-// Select uses a selector to extract an IPLD node or set of nodes from the
-// passed subject node.
-func Select(sel Selector, subject ipld.Node) (ipld.Node, []ipld.Node, error) {
-	return resolve(sel, subject, nil)
-}
-
-func resolve(sel Selector, subject ipld.Node, at []string) (ipld.Node, []ipld.Node, error) {
-	cur := subject
-	for i, seg := range sel {
-		if seg.Identity() {
-			continue
-		} else if seg.Iterator() {
-			if cur != nil && cur.Kind() == datamodel.Kind_List {
-				var many []ipld.Node
-				it := cur.ListIterator()
-				for {
-					if it.Done() {
-						break
-					}
-
-					k, v, err := it.Next()
-					if err != nil {
-						return nil, nil, err
-					}
-
-					key := fmt.Sprintf("%d", k)
-					o, m, err := resolve(sel[i+1:], v, append(at[:], key))
-					if err != nil {
-						return nil, nil, err
-					}
-
-					if m != nil {
-						many = append(many, m...)
-					} else {
-						many = append(many, o)
-					}
-				}
-				return nil, many, nil
-			} else if cur != nil && cur.Kind() == datamodel.Kind_Map {
-				var many []ipld.Node
-				it := cur.MapIterator()
-				for {
-					if it.Done() {
-						break
-					}
-
-					k, v, err := it.Next()
-					if err != nil {
-						return nil, nil, err
-					}
-
-					key, _ := k.AsString()
-					o, m, err := resolve(sel[i+1:], v, append(at[:], key))
-					if err != nil {
-						return nil, nil, err
-					}
-
-					if m != nil {
-						many = append(many, m...)
-					} else {
-						many = append(many, o)
-					}
-				}
-				return nil, many, nil
-			} else if seg.Optional() {
-				cur = nil
-			} else {
-				return nil, nil, newResolutionError(fmt.Sprintf("can not iterate over kind: %s", kindString(cur)), at)
-			}
-
-		} else if seg.Field() != "" {
-			at = append(at, seg.Field())
-			if cur != nil && cur.Kind() == datamodel.Kind_Map {
-				n, err := cur.LookupByString(seg.Field())
-				if err != nil {
-					if isMissing(err) {
-						if seg.Optional() {
-							cur = nil
-						} else {
-							return nil, nil, newResolutionError(fmt.Sprintf("object has no field named: %s", seg.Field()), at)
-						}
-					} else {
-						return nil, nil, err
-					}
-				}
-				cur = n
-			} else if seg.Optional() {
-				cur = nil
-			} else {
-				return nil, nil, newResolutionError(fmt.Sprintf("can not access field: %s on kind: %s", seg.Field(), kindString(cur)), at)
-			}
-		} else if seg.Slice() != nil {
-			if cur != nil && cur.Kind() == datamodel.Kind_List {
-				return nil, nil, newResolutionError("list slice selection not yet implemented", at)
-			} else if cur != nil && cur.Kind() == datamodel.Kind_Bytes {
-				return nil, nil, newResolutionError("bytes slice selection not yet implemented", at)
-			} else if seg.Optional() {
-				cur = nil
-			} else {
-				return nil, nil, newResolutionError(fmt.Sprintf("can not index: %s on kind: %s", seg.Field(), kindString(cur)), at)
-			}
-		} else {
-			at = append(at, fmt.Sprintf("%d", seg.Index()))
-			if cur != nil && cur.Kind() == datamodel.Kind_List {
-				idx := int64(seg.Index())
-				if idx < 0 {
-					idx = cur.Length() + idx
-				}
-				n, err := cur.LookupByIndex(idx)
-				if err != nil {
-					if isMissing(err) {
-						if seg.Optional() {
-							cur = nil
-						} else {
-							return nil, nil, newResolutionError(fmt.Sprintf("index out of bounds: %d", seg.Index()), at)
-						}
-					} else {
-						return nil, nil, err
-					}
-				}
-				cur = n
-			} else if seg.Optional() {
-				cur = nil
-			} else {
-				return nil, nil, newResolutionError(fmt.Sprintf("can not access field: %s on kind: %s", seg.Field(), kindString(cur)), at)
-			}
-		}
-	}
-
-	return cur, nil, nil
-}
-
-func kindString(n datamodel.Node) string {
-	if n == nil {
-		return "null"
-	}
-	return n.Kind().String()
-}
-
-func isMissing(err error) bool {
-	if _, ok := err.(datamodel.ErrNotExists); ok {
-		return true
-	}
-	if _, ok := err.(schema.ErrNoSuchField); ok {
-		return true
-	}
-	if _, ok := err.(schema.ErrInvalidKey); ok {
-		return true
-	}
-	return false
-}
-
-type resolutionerr struct {
-	msg string
-	at  []string
-}
-
-func (r resolutionerr) Name() string {
-	return "ResolutionError"
-}
-
-func (r resolutionerr) Message() string {
-	return fmt.Sprintf("can not resolve path: .%s", strings.Join(r.at, "."))
-}
-
-func (r resolutionerr) At() []string {
-	return r.at
-}
-
-func (r resolutionerr) Error() string {
-	return r.Message()
-}
-
-func newResolutionError(message string, at []string) error {
-	return resolutionerr{message, at}
-}

capability/policy/selector/selector_test.go

@@ -1,499 +0,0 @@
-package selector
-
-import (
-	"fmt"
-	"strings"
-	"testing"
-
-	"github.com/ipld/go-ipld-prime"
-	"github.com/ipld/go-ipld-prime/codec/dagjson"
-	"github.com/ipld/go-ipld-prime/must"
-	basicnode "github.com/ipld/go-ipld-prime/node/basic"
-	"github.com/ipld/go-ipld-prime/node/bindnode"
-	"github.com/ipld/go-ipld-prime/printer"
-	"github.com/stretchr/testify/require"
-)
-
-func TestParse(t *testing.T) {
-	t.Run("identity", func(t *testing.T) {
-		sel, err := Parse(".")
-		require.NoError(t, err)
-		require.Equal(t, 1, len(sel))
-		require.True(t, sel[0].Identity())
-		require.False(t, sel[0].Optional())
-		require.False(t, sel[0].Iterator())
-		require.Empty(t, sel[0].Slice())
-		require.Empty(t, sel[0].Field())
-		require.Empty(t, sel[0].Index())
-	})
-
-	t.Run("field", func(t *testing.T) {
-		sel, err := Parse(".foo")
-		require.NoError(t, err)
-		require.Equal(t, 1, len(sel))
-		require.False(t, sel[0].Identity())
-		require.False(t, sel[0].Optional())
-		require.False(t, sel[0].Iterator())
-		require.Empty(t, sel[0].Slice())
-		require.Equal(t, sel[0].Field(), "foo")
-		require.Empty(t, sel[0].Index())
-	})
-
-	t.Run("explicit field", func(t *testing.T) {
-		sel, err := Parse(`.["foo"]`)
-		require.NoError(t, err)
-		require.Equal(t, 2, len(sel))
-		require.True(t, sel[0].Identity())
-		require.False(t, sel[0].Optional())
-		require.False(t, sel[0].Iterator())
-		require.Empty(t, sel[0].Slice())
-		require.Empty(t, sel[0].Field())
-		require.Empty(t, sel[0].Index())
-		require.False(t, sel[1].Identity())
-		require.False(t, sel[1].Optional())
-		require.False(t, sel[1].Iterator())
-		require.Empty(t, sel[1].Slice())
-		require.Equal(t, sel[1].Field(), "foo")
-		require.Empty(t, sel[1].Index())
-	})
-
-	t.Run("index", func(t *testing.T) {
-		sel, err := Parse(".[138]")
-		require.NoError(t, err)
-		require.Equal(t, 2, len(sel))
-		require.True(t, sel[0].Identity())
-		require.False(t, sel[0].Optional())
-		require.False(t, sel[0].Iterator())
-		require.Empty(t, sel[0].Slice())
-		require.Empty(t, sel[0].Field())
-		require.Empty(t, sel[0].Index())
-		require.False(t, sel[1].Identity())
-		require.False(t, sel[1].Optional())
-		require.False(t, sel[1].Iterator())
-		require.Empty(t, sel[1].Slice())
-		require.Empty(t, sel[1].Field())
-		require.Equal(t, sel[1].Index(), 138)
-	})
-
-	t.Run("negative index", func(t *testing.T) {
-		sel, err := Parse(".[-138]")
-		require.NoError(t, err)
-		require.Equal(t, 2, len(sel))
-		require.True(t, sel[0].Identity())
-		require.False(t, sel[0].Optional())
-		require.False(t, sel[0].Iterator())
-		require.Empty(t, sel[0].Slice())
-		require.Empty(t, sel[0].Field())
-		require.Empty(t, sel[0].Index())
-		require.False(t, sel[1].Identity())
-		require.False(t, sel[1].Optional())
-		require.False(t, sel[1].Iterator())
-		require.Empty(t, sel[1].Slice())
-		require.Empty(t, sel[1].Field())
-		require.Equal(t, sel[1].Index(), -138)
-	})
-
-	t.Run("iterator", func(t *testing.T) {
-		sel, err := Parse(".[]")
-		require.NoError(t, err)
-		require.Equal(t, 2, len(sel))
-		require.True(t, sel[0].Identity())
-		require.False(t, sel[0].Optional())
-		require.False(t, sel[0].Iterator())
-		require.Empty(t, sel[0].Slice())
-		require.Empty(t, sel[0].Field())
-		require.Empty(t, sel[0].Index())
-		require.False(t, sel[1].Identity())
-		require.False(t, sel[1].Optional())
-		require.True(t, sel[1].Iterator())
-		require.Empty(t, sel[1].Slice())
-		require.Empty(t, sel[1].Field())
-		require.Empty(t, sel[1].Index())
-	})
-
-	t.Run("optional field", func(t *testing.T) {
-		sel, err := Parse(".foo?")
-		require.NoError(t, err)
-		require.Equal(t, 1, len(sel))
-		require.False(t, sel[0].Identity())
-		require.True(t, sel[0].Optional())
-		require.False(t, sel[0].Iterator())
-		require.Empty(t, sel[0].Slice())
-		require.Equal(t, sel[0].Field(), "foo")
-		require.Empty(t, sel[0].Index())
-	})
-
-	t.Run("optional explicit field", func(t *testing.T) {
-		sel, err := Parse(`.["foo"]?`)
-		require.NoError(t, err)
-		require.Equal(t, 2, len(sel))
-		require.True(t, sel[0].Identity())
-		require.False(t, sel[0].Optional())
-		require.False(t, sel[0].Iterator())
-		require.Empty(t, sel[0].Slice())
-		require.Empty(t, sel[0].Field())
-		require.Empty(t, sel[0].Index())
-		require.False(t, sel[1].Identity())
-		require.True(t, sel[1].Optional())
-		require.False(t, sel[1].Iterator())
-		require.Empty(t, sel[1].Slice())
-		require.Equal(t, sel[1].Field(), "foo")
-		require.Empty(t, sel[1].Index())
-	})
-
-	t.Run("optional index", func(t *testing.T) {
-		sel, err := Parse(".[138]?")
-		require.NoError(t, err)
-		require.Equal(t, 2, len(sel))
-		require.True(t, sel[0].Identity())
-		require.False(t, sel[0].Optional())
-		require.False(t, sel[0].Iterator())
-		require.Empty(t, sel[0].Slice())
-		require.Empty(t, sel[0].Field())
-		require.Empty(t, sel[0].Index())
-		require.False(t, sel[1].Identity())
-		require.True(t, sel[1].Optional())
-		require.False(t, sel[1].Iterator())
-		require.Empty(t, sel[1].Slice())
-		require.Empty(t, sel[1].Field())
-		require.Equal(t, sel[1].Index(), 138)
-	})
-
-	t.Run("optional iterator", func(t *testing.T) {
-		sel, err := Parse(".[]?")
-		require.NoError(t, err)
-		require.Equal(t, 2, len(sel))
-		require.True(t, sel[0].Identity())
-		require.False(t, sel[0].Optional())
-		require.False(t, sel[0].Iterator())
-		require.Empty(t, sel[0].Slice())
-		require.Empty(t, sel[0].Field())
-		require.Empty(t, sel[0].Index())
-		require.False(t, sel[1].Identity())
-		require.True(t, sel[1].Optional())
-		require.True(t, sel[1].Iterator())
-		require.Empty(t, sel[1].Slice())
-		require.Empty(t, sel[1].Field())
-		require.Empty(t, sel[1].Index())
-	})
-
-	t.Run("nesting", func(t *testing.T) {
-		str := `.foo.["bar"].[138]?.baz[1:]`
-		sel, err := Parse(str)
-		require.NoError(t, err)
-		printSegments(sel)
-		require.Equal(t, str, sel.String())
-		require.Equal(t, 7, len(sel))
-		require.False(t, sel[0].Identity())
-		require.False(t, sel[0].Optional())
-		require.False(t, sel[0].Iterator())
-		require.Empty(t, sel[0].Slice())
-		require.Equal(t, sel[0].Field(), "foo")
-		require.Empty(t, sel[0].Index())
-		require.True(t, sel[1].Identity())
-		require.False(t, sel[1].Optional())
-		require.False(t, sel[1].Iterator())
-		require.Empty(t, sel[1].Slice())
-		require.Empty(t, sel[1].Field())
-		require.Empty(t, sel[1].Index())
-		require.False(t, sel[2].Identity())
-		require.False(t, sel[2].Optional())
-		require.False(t, sel[2].Iterator())
-		require.Empty(t, sel[2].Slice())
-		require.Equal(t, sel[2].Field(), "bar")
-		require.Empty(t, sel[2].Index())
-		require.True(t, sel[3].Identity())
-		require.False(t, sel[3].Optional())
-		require.False(t, sel[3].Iterator())
-		require.Empty(t, sel[3].Slice())
-		require.Empty(t, sel[3].Field())
-		require.Empty(t, sel[3].Index())
-		require.False(t, sel[4].Identity())
-		require.True(t, sel[4].Optional())
-		require.False(t, sel[4].Iterator())
-		require.Empty(t, sel[4].Slice())
-		require.Empty(t, sel[4].Field())
-		require.Equal(t, sel[4].Index(), 138)
-		require.False(t, sel[5].Identity())
-		require.False(t, sel[5].Optional())
-		require.False(t, sel[5].Iterator())
-		require.Empty(t, sel[5].Slice())
-		require.Equal(t, sel[5].Field(), "baz")
-		require.Empty(t, sel[5].Index())
-		require.False(t, sel[6].Identity())
-		require.False(t, sel[6].Optional())
-		require.False(t, sel[6].Iterator())
-		require.Equal(t, sel[6].Slice(), []int{1})
-		require.Empty(t, sel[6].Field())
-		require.Empty(t, sel[6].Index())
-	})
-
-	t.Run("non dotted", func(t *testing.T) {
-		_, err := Parse("foo")
-		require.NotNil(t, err)
-		fmt.Println(err)
-	})
-
-	t.Run("non quoted", func(t *testing.T) {
-		_, err := Parse(".[foo]")
-		require.NotNil(t, err)
-		fmt.Println(err)
-	})
-}
-
-func printSegments(s Selector) {
-	for i, seg := range s {
-		fmt.Printf("%d: %s\n", i, seg.String())
-	}
-}
-
-func TestSelect(t *testing.T) {
-	type name struct {
-		First  string
-		Middle *string
-		Last   string
-	}
-	type interest struct {
-		Name       string
-		Outdoor    bool
-		Experience int
-	}
-	type user struct {
-		Name          name
-		Age           int
-		Nationalities []string
-		Interests     []interest
-	}
-
-	ts, err := ipld.LoadSchemaBytes([]byte(`
-	  type User struct {
-		  name Name
-			age Int
-			nationalities [String]
-			interests [Interest]
-		}
-		type Name struct {
-			first String
-			middle optional String
-			last String
-		}
-		type Interest struct {
-			name String
-			outdoor Bool
-			experience Int
-		}
-	`))
-	require.NoError(t, err)
-	typ := ts.TypeByName("User")
-
-	am := "Joan"
-	alice := user{
-		Name:          name{First: "Alice", Middle: &am, Last: "Wonderland"},
-		Age:           24,
-		Nationalities: []string{"British"},
-		Interests: []interest{
-			{Name: "Cycling", Outdoor: true, Experience: 4},
-			{Name: "Chess", Outdoor: false, Experience: 2},
-		},
-	}
-	bob := user{
-		Name:          name{First: "Bob", Last: "Builder"},
-		Age:           35,
-		Nationalities: []string{"Canadian", "South African"},
-		Interests: []interest{
-			{Name: "Snowboarding", Outdoor: true, Experience: 8},
-			{Name: "Reading", Outdoor: false, Experience: 25},
-		},
-	}
-
-	anode := bindnode.Wrap(&alice, typ)
-	bnode := bindnode.Wrap(&bob, typ)
-
-	t.Run("identity", func(t *testing.T) {
-		sel, err := Parse(".")
-		require.NoError(t, err)
-
-		one, many, err := Select(sel, anode)
-		require.NoError(t, err)
-		require.NotEmpty(t, one)
-		require.Empty(t, many)
-
-		fmt.Println(printer.Sprint(one))
-
-		age := must.Int(must.Node(one.LookupByString("age")))
-		require.Equal(t, int64(alice.Age), age)
-	})
-
-	t.Run("nested property", func(t *testing.T) {
-		sel, err := Parse(".name.first")
-		require.NoError(t, err)
-
-		one, many, err := Select(sel, anode)
-		require.NoError(t, err)
-		require.NotEmpty(t, one)
-		require.Empty(t, many)
-
-		fmt.Println(printer.Sprint(one))
-
-		name := must.String(one)
-		require.Equal(t, alice.Name.First, name)
-
-		one, many, err = Select(sel, bnode)
-		require.NoError(t, err)
-		require.NotEmpty(t, one)
-		require.Empty(t, many)
-
-		fmt.Println(printer.Sprint(one))
-
-		name = must.String(one)
-		require.Equal(t, bob.Name.First, name)
-	})
-
-	t.Run("optional nested property", func(t *testing.T) {
-		sel, err := Parse(".name.middle?")
-		require.NoError(t, err)
-
-		one, many, err := Select(sel, anode)
-		require.NoError(t, err)
-		require.NotEmpty(t, one)
-		require.Empty(t, many)
-
-		fmt.Println(printer.Sprint(one))
-
-		name := must.String(one)
-		require.Equal(t, *alice.Name.Middle, name)
-
-		one, many, err = Select(sel, bnode)
-		require.NoError(t, err)
-		require.Empty(t, one)
-		require.Empty(t, many)
-	})
-
-	t.Run("not exists", func(t *testing.T) {
-		sel, err := Parse(".name.foo")
-		require.NoError(t, err)
-
-		one, many, err := Select(sel, anode)
-		require.Error(t, err)
-		require.Empty(t, one)
-		require.Empty(t, many)
-
-		fmt.Println(err)
-
-		require.ErrorAs(t, err, &resolutionerr{}, "error was not a resolution error")
-	})
-
-	t.Run("optional not exists", func(t *testing.T) {
-		sel, err := Parse(".name.foo?")
-		require.NoError(t, err)
-
-		one, many, err := Select(sel, anode)
-		require.NoError(t, err)
-		require.Empty(t, one)
-		require.Empty(t, many)
-	})
-
-	t.Run("iterator", func(t *testing.T) {
-		sel, err := Parse(".interests[]")
-		require.NoError(t, err)
-
-		one, many, err := Select(sel, anode)
-		require.NoError(t, err)
-		require.Empty(t, one)
-		require.NotEmpty(t, many)
-
-		for _, n := range many {
-			fmt.Println(printer.Sprint(n))
-		}
-
-		iname := must.String(must.Node(many[0].LookupByString("name")))
-		require.Equal(t, alice.Interests[0].Name, iname)
-
-		iname = must.String(must.Node(many[1].LookupByString("name")))
-		require.Equal(t, alice.Interests[1].Name, iname)
-	})
-
-	t.Run("map iterator", func(t *testing.T) {
-		sel, err := Parse(".interests[0][]")
-		require.NoError(t, err)
-
-		one, many, err := Select(sel, anode)
-		require.NoError(t, err)
-		require.Empty(t, one)
-		require.NotEmpty(t, many)
-
-		for _, n := range many {
-			fmt.Println(printer.Sprint(n))
-		}
-
-		require.Equal(t, alice.Interests[0].Name, must.String(many[0]))
-		require.Equal(t, alice.Interests[0].Experience, int(must.Int(many[2])))
-	})
-}
-
-func FuzzParse(f *testing.F) {
-	selectorCorpus := []string{
-		`.`, `.[]`, `.[]?`, `.[][]?`, `.x`, `.["x"]`, `.[0]`, `.[-1]`, `.[0]`,
-		`.[0]`, `.[0:2]`, `.[1:]`, `.[:2]`, `.[0:2]`, `.[1:]`, `.x?`, `.x?`,
-		`.x?`, `.["x"]?`, `.length?`, `.[4]?`, `.[]`, `.[][]`, `.x`, `.x`, `.x`,
-		`.length`, `.[4]`,
-	}
-	for _, selector := range selectorCorpus {
-		f.Add(selector)
-	}
-	f.Fuzz(func(t *testing.T, selector string) {
-		// only look for panic()
-		_, _ = Parse(selector)
-	})
-}
-
-func FuzzParseAndSelect(f *testing.F) {
-	selectorCorpus := []string{
-		`.`, `.[]`, `.[]?`, `.[][]?`, `.x`, `.["x"]`, `.[0]`, `.[-1]`, `.[0]`,
-		`.[0]`, `.[0:2]`, `.[1:]`, `.[:2]`, `.[0:2]`, `.[1:]`, `.x?`, `.x?`,
-		`.x?`, `.["x"]?`, `.length?`, `.[4]?`, `.[]`, `.[][]`, `.x`, `.x`, `.x`,
-		`.length`, `.[4]`,
-	}
-	subjectCorpus := []string{
-		`{"x":1}`, `[1, 2]`, `null`, `[[1], 2, [3]]`, `{"x": 1 }`, `{"x": 1}`,
-		`[1, 2]`, `[1, 2]`, `"Hi"`, `{"/":{"bytes":"AAE"}`, `[0, 1, 2]`,
-		`[0, 1, 2]`, `[0, 1, 2]`, `"hello"`, `{"/":{"bytes":"AAEC"}}`, `{}`,
-		`null`, `[]`, `{}`, `[1, 2]`, `[0, 1]`, `null`, `[[1], 2, [3]]`, `{}`,
-		`null`, `[]`, `[1, 2]`, `[0, 1]`,
-	}
-	for i := 0; ; i++ {
-		switch {
-		case i < len(selectorCorpus) && i < len(subjectCorpus):
-			f.Add(selectorCorpus[i], subjectCorpus[i])
-			continue
-		case i > len(selectorCorpus):
-			f.Add("", subjectCorpus[i])
-			continue
-		case i > len(subjectCorpus):
-			f.Add(selectorCorpus[i], "")
-			continue
-		}
-		break
-	}
-
-	f.Fuzz(func(t *testing.T, selector, subject string) {
-		sel, err := Parse(selector)
-		if err != nil {
-			t.Skip()
-		}
-
-		np := basicnode.Prototype.Any
-		nb := np.NewBuilder()
-		err = dagjson.Decode(nb, strings.NewReader(subject))
-		if err != nil {
-			t.Skip()
-		}
-		node := nb.Build()
-		if node == nil {
-			t.Skip()
-		}
-
-		// look for panic()
-		_, _, _ = Select(sel, node)
-	})
-}

delegation/encoding.go

@@ -1,33 +0,0 @@
-package delegation
-
-import (
-	"github.com/ipld/go-ipld-prime"
-	"github.com/ipld/go-ipld-prime/codec/dagcbor"
-	"github.com/ipld/go-ipld-prime/codec/dagjson"
-)
-
-func (p *PayloadModel) EncodeDagCbor() ([]byte, error) {
-	return ipld.Marshal(dagcbor.Encode, p, PayloadType())
-}
-
-func (p *PayloadModel) EncodeDagJson() ([]byte, error) {
-	return ipld.Marshal(dagjson.Encode, p, PayloadType())
-}
-
-func DecodeDagCbor(data []byte) (*PayloadModel, error) {
-	var p PayloadModel
-	_, err := ipld.Unmarshal(data, dagcbor.Decode, &p, PayloadType())
-	if err != nil {
-		return nil, err
-	}
-	return &p, nil
-}
-
-func DecodeDagJson(data []byte) (*PayloadModel, error) {
-	var p PayloadModel
-	_, err := ipld.Unmarshal(data, dagjson.Decode, &p, PayloadType())
-	if err != nil {
-		return nil, err
-	}
-	return &p, nil
-}

delegation/schema.go

@@ -1,69 +0,0 @@
-package delegation
-
-import (
-	_ "embed"
-	"fmt"
-	"sync"
-
-	"github.com/ipld/go-ipld-prime"
-	"github.com/ipld/go-ipld-prime/datamodel"
-	"github.com/ipld/go-ipld-prime/schema"
-)
-
-//go:embed delegation.ipldsch
-var schemaBytes []byte
-
-var (
-	once sync.Once
-	ts   *schema.TypeSystem
-	err  error
-)
-
-func mustLoadSchema() *schema.TypeSystem {
-	once.Do(func() {
-		ts, err = ipld.LoadSchemaBytes(schemaBytes)
-	})
-	if err != nil {
-		panic(fmt.Errorf("failed to load IPLD schema: %s", err))
-	}
-	return ts
-}
-
-func PayloadType() schema.Type {
-	return mustLoadSchema().TypeByName("Payload")
-}
-
-type PayloadModel struct {
-	// Issuer DID (sender)
-	Iss string
-	// Audience DID (receiver)
-	Aud string
-	// Principal that the chain is about (the Subject)
-	// optional: can be nil
-	Sub *string
-
-	// The Command to eventually invoke
-	Cmd string
-
-	// The delegation policy
-	Pol datamodel.Node
-
-	// A unique, random nonce
-	Nonce []byte
-
-	// Arbitrary Metadata
-	// optional: can be nil
-	Meta MetaModel
-
-	// "Not before" UTC Unix Timestamp in seconds (valid from), 53-bits integer
-	// optional: can be nil
-	Nbf *int64
-	// The timestamp at which the Invocation becomes invalid
-	// optional: can be nil
-	Exp *int64
-}
-
-type MetaModel struct {
-	Keys   []string
-	Values map[string]datamodel.Node
-}

delegation/schema_test.go

@@ -1,71 +0,0 @@
-package delegation
-
-import (
-	"fmt"
-	"testing"
-
-	"github.com/ipld/go-ipld-prime"
-	"github.com/stretchr/testify/require"
-)
-
-func TestSchemaRoundTrip(t *testing.T) {
-	const delegationJson = `
-{
-  "aud":"did:key:def456",
-  "cmd":"/foo/bar",
-  "exp":123456,
-  "iss":"did:key:abc123",
-  "meta":{
-    "bar":"baaar",
-    "foo":"fooo"
-  },
-  "nbf":123456,
-  "nonce":{
-    "/":{
-      "bytes":"c3VwZXItcmFuZG9t"
-    }
-  },
-  "pol":[
-    ["==", ".status", "draft"],
-    ["all", ".reviewer", [
-		["like", ".email", "*@example.com"]]
-	],
-    ["any", ".tags", [ 
-		["or", [
-			["==", ".", "news"], 
-			["==", ".", "press"]]
-      ]]
-	]
-  ],
-  "sub":""
-}
-`
-	// format:    dagJson   -->   PayloadModel   -->   dagCbor   -->   PayloadModel   -->   dagJson
-	// function:      DecodeDagJson()      EncodeDagCbor()   DecodeDagCbor()     EncodeDagJson()
-
-	p1, err := DecodeDagJson([]byte(delegationJson))
-	require.NoError(t, err)
-
-	cborBytes, err := p1.EncodeDagCbor()
-	require.NoError(t, err)
-	fmt.Println("cborBytes length", len(cborBytes))
-	fmt.Println("cbor", string(cborBytes))
-
-	p2, err := DecodeDagCbor(cborBytes)
-	require.NoError(t, err)
-	fmt.Println("read Cbor", p2)
-
-	readJson, err := p2.EncodeDagJson()
-	require.NoError(t, err)
-	fmt.Println("readJson length", len(readJson))
-	fmt.Println("json: ", string(readJson))
-
-	require.JSONEq(t, delegationJson, string(readJson))
-}
-
-func BenchmarkSchemaLoad(b *testing.B) {
-	b.ReportAllocs()
-	for i := 0; i < b.N; i++ {
-		_, _ = ipld.LoadSchemaBytes(schemaBytes)
-	}
-}

delegation/view.go

@@ -1,87 +0,0 @@
-package delegation
-
-import (
-	"fmt"
-	"time"
-
-	"github.com/ipld/go-ipld-prime/datamodel"
-
-	"github.com/ucan-wg/go-ucan/v1/capability/command"
-	"github.com/ucan-wg/go-ucan/v1/capability/policy"
-	"github.com/ucan-wg/go-ucan/v1/did"
-)
-
-type View struct {
-	// Issuer DID (sender)
-	Issuer did.DID
-	// Audience DID (receiver)
-	Audience did.DID
-	// Principal that the chain is about (the Subject)
-	Subject did.DID
-	// The Command to eventually invoke
-	Command *command.Command
-	// The delegation policy
-	Policy policy.Policy
-	// A unique, random nonce
-	Nonce []byte
-	// Arbitrary Metadata
-	Meta map[string]datamodel.Node
-	// "Not before" UTC Unix Timestamp in seconds (valid from), 53-bits integer
-	NotBefore time.Time
-	// The timestamp at which the Invocation becomes invalid
-	Expiration time.Time
-}
-
-// ViewFromModel build a decoded view of the raw IPLD data.
-// This function also serves as validation.
-func ViewFromModel(m PayloadModel) (*View, error) {
-	var view View
-	var err error
-
-	view.Issuer, err = did.Parse(m.Iss)
-	if err != nil {
-		return nil, fmt.Errorf("parse iss: %w", err)
-	}
-
-	view.Audience, err = did.Parse(m.Aud)
-	if err != nil {
-		return nil, fmt.Errorf("parse audience: %w", err)
-	}
-
-	if m.Sub != nil {
-		view.Subject, err = did.Parse(*m.Sub)
-		if err != nil {
-			return nil, fmt.Errorf("parse subject: %w", err)
-		}
-	} else {
-		view.Subject = did.Undef
-	}
-
-	view.Command, err = command.Parse(m.Cmd)
-	if err != nil {
-		return nil, fmt.Errorf("parse command: %w", err)
-	}
-
-	view.Policy, err = policy.FromIPLD(m.Pol)
-	if err != nil {
-		return nil, fmt.Errorf("parse policy: %w", err)
-	}
-
-	if len(m.Nonce) == 0 {
-		return nil, fmt.Errorf("nonce is required")
-	}
-	view.Nonce = m.Nonce
-
-	// TODO: copy?
-	view.Meta = m.Meta.Values
-
-	if m.Nbf != nil {
-		view.NotBefore = time.Unix(*m.Nbf, 0)
-	}
-
-	if m.Exp != nil {
-		view.Expiration = time.Unix(*m.Exp, 0)
-	}
-
-	return &view, nil
-}

did/did.go

@@ -1,86 +0,0 @@
-package did
-
-import (
-	"fmt"
-	"strings"
-
-	mbase "github.com/multiformats/go-multibase"
-	varint "github.com/multiformats/go-varint"
-)
-
-const Prefix = "did:"
-const KeyPrefix = "did:key:"
-
-const DIDCore = 0x0d1d
-const Ed25519 = 0xed
-
-var MethodOffset = varint.UvarintSize(uint64(DIDCore))
-
-type DID struct {
-	key bool
-	str string
-}
-
-// Undef can be used to represent a nil or undefined DID, using DID{}
-// directly is also acceptable.
-var Undef = DID{}
-
-func (d DID) Defined() bool {
-	return d.str != ""
-}
-
-func (d DID) Bytes() []byte {
-	if !d.Defined() {
-		return nil
-	}
-	return []byte(d.str)
-}
-
-func (d DID) DID() DID {
-	return d
-}
-
-// String formats the decentralized identity document (DID) as a string.
-func (d DID) String() string {
-	if d.key {
-		key, _ := mbase.Encode(mbase.Base58BTC, []byte(d.str))
-		return "did:key:" + key
-	}
-	return "did:" + d.str[MethodOffset:]
-}
-
-func Decode(bytes []byte) (DID, error) {
-	code, _, err := varint.FromUvarint(bytes)
-	if err != nil {
-		return Undef, err
-	}
-	if code == Ed25519 {
-		return DID{str: string(bytes), key: true}, nil
-	} else if code == DIDCore {
-		return DID{str: string(bytes)}, nil
-	}
-	return Undef, fmt.Errorf("unsupported DID encoding: 0x%x", code)
-}
-
-func Parse(str string) (DID, error) {
-	if !strings.HasPrefix(str, Prefix) {
-		return Undef, fmt.Errorf("must start with 'did:'")
-	}
-
-	if strings.HasPrefix(str, KeyPrefix) {
-		code, bytes, err := mbase.Decode(str[len(KeyPrefix):])
-		if err != nil {
-			return Undef, err
-		}
-		if code != mbase.Base58BTC {
-			return Undef, fmt.Errorf("not Base58BTC encoded")
-		}
-		return Decode(bytes)
-	}
-
-	buf := make([]byte, MethodOffset)
-	varint.PutUvarint(buf, DIDCore)
-	suffix, _ := strings.CutPrefix(str, Prefix)
-	buf = append(buf, suffix...)
-	return DID{str: string(buf)}, nil
-}

did/did_test.go

@@ -1,79 +0,0 @@
-package did
-
-import (
-	"testing"
-)
-
-func TestParseDIDKey(t *testing.T) {
-	str := "did:key:z6Mkod5Jr3yd5SC7UDueqK4dAAw5xYJYjksy722tA9Boxc4z"
-	d, err := Parse(str)
-	if err != nil {
-		t.Fatalf("%v", err)
-	}
-	if d.String() != str {
-		t.Fatalf("expected %v to equal %v", d.String(), str)
-	}
-}
-
-func TestDecodeDIDKey(t *testing.T) {
-	str := "did:key:z6Mkod5Jr3yd5SC7UDueqK4dAAw5xYJYjksy722tA9Boxc4z"
-	d0, err := Parse(str)
-	if err != nil {
-		t.Fatalf("%v", err)
-	}
-	d1, err := Decode(d0.Bytes())
-	if err != nil {
-		t.Fatalf("%v", err)
-	}
-	if d1.String() != str {
-		t.Fatalf("expected %v to equal %v", d1.String(), str)
-	}
-}
-
-func TestParseDIDWeb(t *testing.T) {
-	str := "did:web:up.web3.storage"
-	d, err := Parse(str)
-	if err != nil {
-		t.Fatalf("%v", err)
-	}
-	if d.String() != str {
-		t.Fatalf("expected %v to equal %v", d.String(), str)
-	}
-}
-
-func TestDecodeDIDWeb(t *testing.T) {
-	str := "did:web:up.web3.storage"
-	d0, err := Parse(str)
-	if err != nil {
-		t.Fatalf("%v", err)
-	}
-	d1, err := Decode(d0.Bytes())
-	if err != nil {
-		t.Fatalf("%v", err)
-	}
-	if d1.String() != str {
-		t.Fatalf("expected %v to equal %v", d1.String(), str)
-	}
-}
-
-func TestEquivalence(t *testing.T) {
-	u0 := DID{}
-	u1 := Undef
-	if u0 != u1 {
-		t.Fatalf("undef DID not equivalent")
-	}
-
-	d0, err := Parse("did:key:z6Mkod5Jr3yd5SC7UDueqK4dAAw5xYJYjksy722tA9Boxc4z")
-	if err != nil {
-		t.Fatalf("%v", err)
-	}
-
-	d1, err := Parse("did:key:z6Mkod5Jr3yd5SC7UDueqK4dAAw5xYJYjksy722tA9Boxc4z")
-	if err != nil {
-		t.Fatalf("%v", err)
-	}
-
-	if d0 != d1 {
-		t.Fatalf("two equivalent DID not equivalent")
-	}
-}

go.mod

@@ -1,31 +1,36 @@
-module github.com/ucan-wg/go-ucan/v1
+module github.com/ucan-wg/go-ucan
 
-go 1.21
+go 1.24.4
 
-toolchain go1.22.1
+toolchain go1.24.5
 
 require (
-	github.com/gobwas/glob v0.2.3
+	github.com/MetaMask/go-did-it v1.0.0-pre1
-	github.com/ipfs/go-cid v0.4.1
+	github.com/avast/retry-go/v4 v4.6.1
+	github.com/ipfs/go-cid v0.5.0
 	github.com/ipld/go-ipld-prime v0.21.0
-	github.com/multiformats/go-multibase v0.0.3
+	github.com/multiformats/go-multibase v0.2.0
-	github.com/multiformats/go-varint v0.0.6
+	github.com/multiformats/go-multicodec v0.9.0
-	github.com/stretchr/testify v1.9.0
+	github.com/multiformats/go-multihash v0.2.3
+	github.com/multiformats/go-varint v0.0.7
+	github.com/stretchr/testify v1.10.0
+	github.com/ucan-wg/go-varsig v1.0.0
+	golang.org/x/crypto v0.40.0
 )
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/klauspost/cpuid/v2 v2.0.9 // indirect
+	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.4.0 // indirect
-	github.com/minio/sha256-simd v1.0.0 // indirect
+	github.com/klauspost/cpuid/v2 v2.2.9 // indirect
+	github.com/minio/sha256-simd v1.0.1 // indirect
 	github.com/mr-tron/base58 v1.2.0 // indirect
-	github.com/multiformats/go-base32 v0.0.3 // indirect
+	github.com/multiformats/go-base32 v0.1.0 // indirect
-	github.com/multiformats/go-base36 v0.1.0 // indirect
+	github.com/multiformats/go-base36 v0.2.0 // indirect
-	github.com/multiformats/go-multihash v0.2.3 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/polydawn/refmt v0.89.0 // indirect
 	github.com/spaolacci/murmur3 v1.1.0 // indirect
-	golang.org/x/crypto v0.1.0 // indirect
+	golang.org/x/sys v0.34.0 // indirect
-	golang.org/x/sys v0.1.0 // indirect
+	gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
-	lukechampine.com/blake3 v1.1.6 // indirect
+	lukechampine.com/blake3 v1.3.0 // indirect
 )

go.sum

@@ -1,46 +1,50 @@
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/MetaMask/go-did-it v1.0.0-pre1 h1:NTGAC7z52TwFegEF7c+csUr/6Al1nAo6ValAAxOsjto=
+github.com/MetaMask/go-did-it v1.0.0-pre1/go.mod h1:7m9syDnXFTg5GmUEcydpO4Rs3eYT4McFH7vCw5fp3A4=
+github.com/avast/retry-go/v4 v4.6.1 h1:VkOLRubHdisGrHnTu89g08aQEWEgRU7LVEop3GbIcMk=
+github.com/avast/retry-go/v4 v4.6.1/go.mod h1:V6oF8njAwxJ5gRo1Q7Cxab24xs5NCWZBeaHHBklR8mA=
 github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/decred/dcrd/crypto/blake256 v1.1.0 h1:zPMNGQCm0g4QTY27fOCorQW7EryeQ/U0x++OzVrdms8=
+github.com/decred/dcrd/crypto/blake256 v1.1.0/go.mod h1:2OfgNZ5wDpcsFmHmCK5gZTPcCXqlm2ArzUIkw9czNJo=
+github.com/decred/dcrd/dcrec/secp256k1/v4 v4.4.0 h1:NMZiJj8QnKe1LgsbDayM4UoHwbvwDRwnI3hwNaAHRnc=
+github.com/decred/dcrd/dcrec/secp256k1/v4 v4.4.0/go.mod h1:ZXNYxsqcloTdSy/rNShjYzMhyjf0LaoftYK0p+A3h40=
 github.com/frankban/quicktest v1.14.6 h1:7Xjx+VpznH+oBnejlPUj8oUpdxnVs4f8XU8WnHkI4W8=
 github.com/frankban/quicktest v1.14.6/go.mod h1:4ptaffx2x8+WTWXmUCuVU6aPUX1/Mz7zb5vbUoiM6w0=
 github.com/go-yaml/yaml v2.1.0+incompatible/go.mod h1:w2MrLa16VYP0jy6N7M5kHaCkaLENm+P+Tv+MfurjSw0=
-github.com/gobwas/glob v0.2.3 h1:A4xDbljILXROh+kObIiy5kIaPYD8e96x1tgBhUI5J+Y=
-github.com/gobwas/glob v0.2.3/go.mod h1:d3Ez4x06l9bZtSvzIay5+Yzi0fmZzPgnTbPcKjJAkT8=
 github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
 github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/gopherjs/gopherjs v0.0.0-20181017120253-0766667cb4d1 h1:EGx4pi6eqNxGaHF6qqu48+N2wcFQ5qg5FXgOdqsJ5d8=
 github.com/gopherjs/gopherjs v0.0.0-20181017120253-0766667cb4d1/go.mod h1:wJfORRmW1u3UXTncJ5qlYoELFm8eSnnEO6hX4iZ3EWY=
-github.com/ipfs/go-cid v0.4.1 h1:A/T3qGvxi4kpKWWcPC/PgbvDA2bjVLO7n4UeVwnbs/s=
+github.com/ipfs/go-cid v0.5.0 h1:goEKKhaGm0ul11IHA7I6p1GmKz8kEYniqFopaB5Otwg=
-github.com/ipfs/go-cid v0.4.1/go.mod h1:uQHwDeX4c6CtyrFwdqyhpNcxVewur1M7l7fNU7LKwZk=
+github.com/ipfs/go-cid v0.5.0/go.mod h1:0L7vmeNXpQpUS9vt+yEARkJ8rOg43DF3iPgn4GIN0mk=
 github.com/ipld/go-ipld-prime v0.21.0 h1:n4JmcpOlPDIxBcY037SVfpd1G+Sj1nKZah0m6QH9C2E=
 github.com/ipld/go-ipld-prime v0.21.0/go.mod h1:3RLqy//ERg/y5oShXXdx5YIp50cFGOanyMctpPjsvxQ=
 github.com/jtolds/gls v4.20.0+incompatible h1:xdiiI2gbIgH/gLH7ADydsJ1uDOEzR8yvV7C0MuV77Wo=
 github.com/jtolds/gls v4.20.0+incompatible/go.mod h1:QJZ7F/aHp+rZTRtaJ1ow/lLfFfVYBRgL+9YlvaHOwJU=
-github.com/klauspost/cpuid/v2 v2.0.4/go.mod h1:FInQzS24/EEf25PyTYn52gqo7WaD8xa0213Md/qVLRg=
+github.com/klauspost/cpuid/v2 v2.2.9 h1:66ze0taIn2H33fBvCkXuv9BmCwDfafmiIVpKV9kKGuY=
-github.com/klauspost/cpuid/v2 v2.0.9 h1:lgaqFMSdTdQYdZ04uHyN2d/eKdOMyi2YLSvlQIBFYa4=
+github.com/klauspost/cpuid/v2 v2.2.9/go.mod h1:rqkxqrZ1EhYM9G+hXH7YdowN5R5RGN6NK4QwQ3WMXF8=
-github.com/klauspost/cpuid/v2 v2.0.9/go.mod h1:FInQzS24/EEf25PyTYn52gqo7WaD8xa0213Md/qVLRg=
 github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
 github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
-github.com/minio/sha256-simd v1.0.0 h1:v1ta+49hkWZyvaKwrQB8elexRqm6Y0aMLjCNsrYxo6g=
+github.com/minio/sha256-simd v1.0.1 h1:6kaan5IFmwTNynnKKpDHe6FWHohJOHhCPchzK49dzMM=
-github.com/minio/sha256-simd v1.0.0/go.mod h1:OuYzVNI5vcoYIAmbIvHPl3N3jUzVedXbKy5RFepssQM=
+github.com/minio/sha256-simd v1.0.1/go.mod h1:Pz6AKMiUdngCLpeTL/RJY1M9rUuPMYujV5xJjtbRSN8=
-github.com/mr-tron/base58 v1.1.0/go.mod h1:xcD2VGqlgYjBdcBLw+TuYLr8afG+Hj8g2eTVqeSzSU8=
 github.com/mr-tron/base58 v1.2.0 h1:T/HDJBh4ZCPbU39/+c3rRvE0uKBQlU27+QI8LJ4t64o=
 github.com/mr-tron/base58 v1.2.0/go.mod h1:BinMc/sQntlIE1frQmRFPUoPA1Zkr8VRgBdjWI2mNwc=
-github.com/multiformats/go-base32 v0.0.3 h1:tw5+NhuwaOjJCC5Pp82QuXbrmLzWg7uxlMFp8Nq/kkI=
+github.com/multiformats/go-base32 v0.1.0 h1:pVx9xoSPqEIQG8o+UbAe7DNi51oej1NtK+aGkbLYxPE=
-github.com/multiformats/go-base32 v0.0.3/go.mod h1:pLiuGC8y0QR3Ue4Zug5UzK9LjgbkL8NSQj0zQ5Nz/AA=
+github.com/multiformats/go-base32 v0.1.0/go.mod h1:Kj3tFY6zNr+ABYMqeUNeGvkIC/UYgtWibDcT0rExnbI=
-github.com/multiformats/go-base36 v0.1.0 h1:JR6TyF7JjGd3m6FbLU2cOxhC0Li8z8dLNGQ89tUg4F4=
+github.com/multiformats/go-base36 v0.2.0 h1:lFsAbNOGeKtuKozrtBsAkSVhv1p9D0/qedU9rQyccr0=
-github.com/multiformats/go-base36 v0.1.0/go.mod h1:kFGE83c6s80PklsHO9sRn2NCoffoRdUUOENyW/Vv6sM=
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 github.com/multiformats/go-multicodec v0.9.0/go.mod h1:L3QTQvMIaVBkXOXXtVmYE+LI16i14xuaojr/H7Ai54k=
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 github.com/multiformats/go-multihash v0.2.3/go.mod h1:dXgKXCXjBzdscBLk9JkjINiEsCKRVch90MdaGiKsvSM=
-github.com/multiformats/go-varint v0.0.6 h1:gk85QWKxh3TazbLxED/NlDVv8+q+ReFJk7Y2W/KhfNY=
+github.com/multiformats/go-varint v0.0.7 h1:sWSGR+f/eu5ABZA2ZpYKBILXTTs9JWpdEM/nEGOHFS8=
-github.com/multiformats/go-varint v0.0.6/go.mod h1:3Ls8CIEsrijN6+B7PbrXRPxHRPuXSrVKRY101jdMZYE=
+github.com/multiformats/go-varint v0.0.7/go.mod h1:r8PUYw/fD/SjBCiKOoDlGF6QawOELpZAu9eioSos/OU=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/polydawn/refmt v0.89.0 h1:ADJTApkvkeBZsN0tBTx8QjpD9JkmxbKp0cxfr9qszm4=
@@ -55,26 +59,29 @@ github.com/smartystreets/goconvey v1.7.2 h1:9RBaZCeXEQ3UselpuwUQHltGVXvdwm6cv1hg
 github.com/smartystreets/goconvey v1.7.2/go.mod h1:Vw0tHAZW6lzCRk3xgdin6fKYcG+G3Pg9vgXWeJpQFMM=
 github.com/spaolacci/murmur3 v1.1.0 h1:7c1g84S4BPRrfL5Xrdp6fOJ206sU9y293DDHaoy0bLI=
 github.com/spaolacci/murmur3 v1.1.0/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
-github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
+github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
-github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+github.com/ucan-wg/go-varsig v1.0.0 h1:Hrc437Zg+B5Eoajg+qZQZI3Q3ocPyjlnp3/Bz9ZnlWw=
+github.com/ucan-wg/go-varsig v1.0.0/go.mod h1:Sakln6IPooDPH+ClQ0VvR09TuwUhHcfLqcPiPkMZGh0=
 github.com/urfave/cli v1.22.10/go.mod h1:Gos4lmkARVdJ6EkW0WaNv/tZAAMe9V7XWyB60NtXRu0=
 github.com/warpfork/go-wish v0.0.0-20220906213052-39a1cc7a02d0 h1:GDDkbFiaK8jsSDJfjId/PEGEShv6ugrt4kYsC5UIDaQ=
 github.com/warpfork/go-wish v0.0.0-20220906213052-39a1cc7a02d0/go.mod h1:x6AKhvSSexNrVSrViXSHUEbICjmGXhtgABaHIySUSGw=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.1.0 h1:MDRAIl0xIo9Io2xV565hzXHw3zVseKrJKodhohM5CjU=
+golang.org/x/crypto v0.40.0 h1:r4x+VvoG5Fm+eJcxMaY8CQM7Lb0l1lsmjGBQ6s8BfKM=
-golang.org/x/crypto v0.1.0/go.mod h1:RecgLatLF4+eUMCP1PoPZQb+cVrJcOPbHkTkbkB9sbw=
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 golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
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-golang.org/x/sys v0.1.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
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 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/tools v0.0.0-20190328211700-ab21143f2384/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
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pkg/args/args.go

@@ -0,0 +1,187 @@
+// Package args provides the type that represents the Arguments passed to
+// a command within an invocation.Token as well as a convenient Add method
+// to incrementally build the underlying map.
+package args
+
+import (
+	"errors"
+	"fmt"
+	"iter"
+	"sort"
+	"strings"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/datamodel"
+	"github.com/ipld/go-ipld-prime/fluent/qp"
+	"github.com/ipld/go-ipld-prime/node/basicnode"
+	"github.com/ipld/go-ipld-prime/printer"
+
+	"github.com/ucan-wg/go-ucan/pkg/policy/limits"
+	"github.com/ucan-wg/go-ucan/pkg/policy/literal"
+)
+
+var ErrNotFound = errors.New("key not found in meta")
+
+// Args are the Command's arguments when an invocation Token is processed by the executor.
+// This also serves as a way to construct the underlying IPLD data with minimum allocations
+// and transformations, while hiding the IPLD complexity from the caller.
+type Args struct {
+	// This type must be compatible with the IPLD type represented by the IPLD
+	// schema { String : Any }.
+
+	Keys   []string
+	Values map[string]ipld.Node
+}
+
+// New returns a pointer to an initialized Args value.
+func New() *Args {
+	return &Args{
+		Values: map[string]ipld.Node{},
+	}
+}
+
+// GetNode retrieves a value as a raw IPLD node.
+// Returns ErrNotFound if the given key is missing.
+func (a *Args) GetNode(key string) (ipld.Node, error) {
+	v, ok := a.Values[key]
+	if !ok {
+		return nil, ErrNotFound
+	}
+	return v, nil
+}
+
+// Add inserts a key/value pair in the Args set.
+//
+// Accepted types for val are any CBOR compatible type, or directly IPLD values.
+func (a *Args) Add(key string, val any) error {
+	if _, ok := a.Values[key]; ok {
+		return fmt.Errorf("duplicate key %q", key)
+	}
+
+	node, err := literal.Any(val)
+	if err != nil {
+		return err
+	}
+
+	if err := limits.ValidateIntegerBoundsIPLD(node); err != nil {
+		return fmt.Errorf("value for key %q: %w", key, err)
+	}
+
+	a.Values[key] = node
+	a.Keys = append(a.Keys, key)
+
+	return nil
+}
+
+type Iterator interface {
+	Iter() iter.Seq2[string, ipld.Node]
+}
+
+// Include merges the provided arguments into the existing arguments.
+//
+// If duplicate keys are encountered, the new value is silently dropped
+// without causing an error.
+func (a *Args) Include(other Iterator) {
+	for key, value := range other.Iter() {
+		if _, ok := a.Values[key]; ok {
+			// don't overwrite
+			continue
+		}
+		a.Values[key] = value
+		a.Keys = append(a.Keys, key)
+	}
+}
+
+// Len return the number of arguments.
+func (a *Args) Len() int {
+	return len(a.Keys)
+}
+
+// Iter iterates over the args key/values
+func (a *Args) Iter() iter.Seq2[string, ipld.Node] {
+	return func(yield func(string, ipld.Node) bool) {
+		for _, key := range a.Keys {
+			if !yield(key, a.Values[key]) {
+				return
+			}
+		}
+	}
+}
+
+// ToIPLD wraps an instance of an Args with an ipld.Node.
+func (a *Args) ToIPLD() (ipld.Node, error) {
+	sort.Strings(a.Keys)
+
+	return qp.BuildMap(basicnode.Prototype.Any, int64(len(a.Keys)), func(ma datamodel.MapAssembler) {
+		for _, key := range a.Keys {
+			qp.MapEntry(ma, key, qp.Node(a.Values[key]))
+		}
+	})
+}
+
+// Equals tells if two Args hold the same values.
+func (a *Args) Equals(other *Args) bool {
+	if len(a.Keys) != len(other.Keys) {
+		return false
+	}
+	if len(a.Values) != len(other.Values) {
+		return false
+	}
+	for _, key := range a.Keys {
+		if !ipld.DeepEqual(a.Values[key], other.Values[key]) {
+			return false
+		}
+	}
+	return true
+}
+
+func (a *Args) String() string {
+	sort.Strings(a.Keys)
+
+	buf := strings.Builder{}
+	buf.WriteString("{")
+
+	for _, key := range a.Keys {
+		buf.WriteString("\n\t")
+		buf.WriteString(key)
+		buf.WriteString(": ")
+		buf.WriteString(strings.ReplaceAll(printer.Sprint(a.Values[key]), "\n", "\n\t"))
+		buf.WriteString(",")
+	}
+
+	if len(a.Keys) > 0 {
+		buf.WriteString("\n")
+	}
+	buf.WriteString("}")
+
+	return buf.String()
+}
+
+// ReadOnly returns a read-only version of Args.
+func (a *Args) ReadOnly() ReadOnly {
+	return ReadOnly{args: a}
+}
+
+// Clone makes a deep copy.
+func (a *Args) Clone() *Args {
+	res := &Args{
+		Keys:   make([]string, len(a.Keys)),
+		Values: make(map[string]ipld.Node, len(a.Values)),
+	}
+	copy(res.Keys, a.Keys)
+	for k, v := range a.Values {
+		res.Values[k] = v
+	}
+	return res
+}
+
+// Validate checks that all values in the Args are valid according to UCAN specs
+func (a *Args) Validate() error {
+	for key, value := range a.Values {
+		if err := limits.ValidateIntegerBoundsIPLD(value); err != nil {
+			return fmt.Errorf("value for key %q: %w", key, err)
+		}
+	}
+
+	return nil
+}

pkg/args/args_test.go

@@ -0,0 +1,297 @@
+package args_test
+
+import (
+	"maps"
+	"sync"
+	"testing"
+
+	"github.com/ipfs/go-cid"
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/codec/dagcbor"
+	"github.com/ipld/go-ipld-prime/datamodel"
+	"github.com/ipld/go-ipld-prime/node/basicnode"
+	"github.com/ipld/go-ipld-prime/schema"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/ucan-wg/go-ucan/pkg/args"
+	"github.com/ucan-wg/go-ucan/pkg/policy/limits"
+	"github.com/ucan-wg/go-ucan/pkg/policy/literal"
+)
+
+func TestArgs(t *testing.T) {
+	t.Parallel()
+
+	const (
+		intKey    = "intKey"
+		mapKey    = "mapKey"
+		nilKey    = "nilKey"
+		boolKey   = "boolKey"
+		linkKey   = "linkKey"
+		listKey   = "listKey"
+		nodeKey   = "nodeKey"
+		uintKey   = "uintKey"
+		bytesKey  = "bytesKey"
+		floatKey  = "floatKey"
+		stringKey = "stringKey"
+	)
+
+	const (
+		expIntVal    = int64(-42)
+		expBoolVal   = true
+		expUintVal   = uint(42)
+		expStringVal = "stringVal"
+	)
+
+	var (
+		expMapVal = map[string]string{"keyOne": "valOne", "keyTwo": "valTwo"}
+		// expNilVal = (map[string]string)(nil)
+		expLinkVal  = cid.MustParse("bafzbeigai3eoy2ccc7ybwjfz5r3rdxqrinwi4rwytly24tdbh6yk7zslrm")
+		expListVal  = []string{"elem1", "elem2", "elem3"}
+		expNodeVal  = literal.String("nodeVal")
+		expBytesVal = []byte{0xde, 0xad, 0xbe, 0xef}
+		expFloatVal = 42.0
+	)
+
+	argsIn := args.New()
+
+	for _, a := range []struct {
+		key string
+		val any
+	}{
+		{key: intKey, val: expIntVal},
+		{key: mapKey, val: expMapVal},
+		// {key:  nilKey, val: expNilVal},
+		{key: boolKey, val: expBoolVal},
+		{key: linkKey, val: expLinkVal},
+		{key: listKey, val: expListVal},
+		{key: uintKey, val: expUintVal},
+		{key: nodeKey, val: expNodeVal},
+		{key: bytesKey, val: expBytesVal},
+		{key: floatKey, val: expFloatVal},
+		{key: stringKey, val: expStringVal},
+	} {
+		require.NoError(t, argsIn.Add(a.key, a.val))
+	}
+
+	// Round-trip to DAG-CBOR
+	argsOut := roundTripThroughDAGCBOR(t, argsIn)
+	assert.ElementsMatch(t, argsIn.Keys, argsOut.Keys)
+	assert.Equal(t, argsIn.Values, argsOut.Values)
+
+	actMapVal := map[string]string{}
+	mit := argsOut.Values[mapKey].MapIterator()
+
+	for !mit.Done() {
+		k, v, err := mit.Next()
+		require.NoError(t, err)
+		ks := must(k.AsString())
+		vs := must(v.AsString())
+		actMapVal[ks] = vs
+	}
+
+	actListVal := []string{}
+	lit := argsOut.Values[listKey].ListIterator()
+
+	for !lit.Done() {
+		_, v, err := lit.Next()
+		require.NoError(t, err)
+		vs := must(v.AsString())
+
+		actListVal = append(actListVal, vs)
+	}
+
+	assert.Equal(t, expIntVal, must(argsOut.Values[intKey].AsInt()))
+	assert.Equal(t, expMapVal, actMapVal) // TODO: special accessor
+	// TODO: the nil map comes back empty (but the right type)
+	// assert.Equal(t, expNilVal, actNilVal)
+	assert.Equal(t, expBoolVal, must(argsOut.Values[boolKey].AsBool()))
+	assert.Equal(t, expLinkVal.String(), must(argsOut.Values[linkKey].AsLink()).(datamodel.Link).String()) // TODO: special accessor
+	assert.Equal(t, expListVal, actListVal)                                                                // TODO: special accessor
+	assert.Equal(t, expNodeVal, argsOut.Values[nodeKey])
+	assert.Equal(t, expUintVal, uint(must(argsOut.Values[uintKey].AsInt())))
+	assert.Equal(t, expBytesVal, must(argsOut.Values[bytesKey].AsBytes()))
+	assert.Equal(t, expFloatVal, must(argsOut.Values[floatKey].AsFloat()))
+	assert.Equal(t, expStringVal, must(argsOut.Values[stringKey].AsString()))
+}
+
+func TestArgs_Include(t *testing.T) {
+	t.Parallel()
+
+	argsIn := args.New()
+	require.NoError(t, argsIn.Add("key1", "val1"))
+	require.NoError(t, argsIn.Add("key2", "val2"))
+
+	argsOther := args.New()
+	require.NoError(t, argsOther.Add("key2", "valOther")) // This should not overwrite key2 above
+	require.NoError(t, argsOther.Add("key3", "val3"))
+	require.NoError(t, argsOther.Add("key4", "val4"))
+
+	argsIn.Include(argsOther)
+
+	assert.Len(t, argsIn.Values, 4)
+	assert.Equal(t, "val1", must(argsIn.Values["key1"].AsString()))
+	assert.Equal(t, "val2", must(argsIn.Values["key2"].AsString()))
+	assert.Equal(t, "val3", must(argsIn.Values["key3"].AsString()))
+	assert.Equal(t, "val4", must(argsIn.Values["key4"].AsString()))
+}
+
+func TestIterCloneEquals(t *testing.T) {
+	a := args.New()
+
+	require.NoError(t, a.Add("foo", "bar"))
+	require.NoError(t, a.Add("baz", 1234))
+
+	expected := map[string]ipld.Node{
+		"foo": basicnode.NewString("bar"),
+		"baz": basicnode.NewInt(1234),
+	}
+
+	// args -> iter
+	require.Equal(t, expected, maps.Collect(a.Iter()))
+
+	// readonly -> iter
+	ro := a.ReadOnly()
+	require.Equal(t, expected, maps.Collect(ro.Iter()))
+
+	// args -> clone -> iter
+	clone := a.Clone()
+	require.Equal(t, expected, maps.Collect(clone.Iter()))
+
+	// readonly -> WriteableClone -> iter
+	wclone := ro.WriteableClone()
+	require.Equal(t, expected, maps.Collect(wclone.Iter()))
+
+	require.True(t, a.Equals(wclone))
+	require.True(t, ro.Equals(wclone.ReadOnly()))
+}
+
+func TestInclude(t *testing.T) {
+	a1 := args.New()
+
+	require.NoError(t, a1.Add("samekey", "bar"))
+	require.NoError(t, a1.Add("baz", 1234))
+
+	a2 := args.New()
+
+	require.NoError(t, a2.Add("samekey", "othervalue")) // check no overwrite
+	require.NoError(t, a2.Add("otherkey", 1234))
+
+	a1.Include(a2)
+
+	require.Equal(t, map[string]ipld.Node{
+		"samekey":  basicnode.NewString("bar"),
+		"baz":      basicnode.NewInt(1234),
+		"otherkey": basicnode.NewInt(1234),
+	}, maps.Collect(a1.Iter()))
+}
+
+func TestArgsIntegerBounds(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		key     string
+		val     int64
+		wantErr string
+	}{
+		{
+			name: "valid int",
+			key:  "valid",
+			val:  42,
+		},
+		{
+			name: "max safe integer",
+			key:  "max",
+			val:  limits.MaxInt53,
+		},
+		{
+			name: "min safe integer",
+			key:  "min",
+			val:  limits.MinInt53,
+		},
+		{
+			name:    "exceeds max safe integer",
+			key:     "tooBig",
+			val:     limits.MaxInt53 + 1,
+			wantErr: "exceeds safe integer bounds",
+		},
+		{
+			name:    "below min safe integer",
+			key:     "tooSmall",
+			val:     limits.MinInt53 - 1,
+			wantErr: "exceeds safe integer bounds",
+		},
+		{
+			name:    "duplicate key",
+			key:     "duplicate",
+			val:     42,
+			wantErr: "duplicate key",
+		},
+	}
+
+	a := args.New()
+	require.NoError(t, a.Add("duplicate", 1)) // tests duplicate key
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := a.Add(tt.key, tt.val)
+			if tt.wantErr != "" {
+				require.Error(t, err)
+				require.Contains(t, err.Error(), tt.wantErr)
+			} else {
+				require.NoError(t, err)
+				val, err := a.GetNode(tt.key)
+				require.NoError(t, err)
+				i, err := val.AsInt()
+				require.NoError(t, err)
+				require.Equal(t, tt.val, i)
+			}
+		})
+	}
+}
+
+const (
+	argsSchema = "type Args { String : Any }"
+	argsName   = "Args"
+)
+
+var (
+	once      sync.Once
+	ts        *schema.TypeSystem
+	errSchema error
+)
+
+func argsType() schema.Type {
+	once.Do(func() {
+		ts, errSchema = ipld.LoadSchemaBytes([]byte(argsSchema))
+	})
+	if errSchema != nil {
+		panic(errSchema)
+	}
+
+	return ts.TypeByName(argsName)
+}
+
+func roundTripThroughDAGCBOR(t *testing.T, argsIn *args.Args) *args.Args {
+	t.Helper()
+
+	node, err := argsIn.ToIPLD()
+	require.NoError(t, err)
+
+	data, err := ipld.Encode(node, dagcbor.Encode)
+	require.NoError(t, err)
+
+	var argsOut args.Args
+	_, err = ipld.Unmarshal(data, dagcbor.Decode, &argsOut, argsType())
+	require.NoError(t, err)
+
+	return &argsOut
+}
+
+func must[T any](t T, err error) T {
+	if err != nil {
+		panic(err)
+	}
+	return t
+}

pkg/args/builder.go

@@ -0,0 +1,71 @@
+package args
+
+import (
+	"errors"
+
+	"github.com/ipld/go-ipld-prime"
+)
+
+// Builder allows the fluid construction of an Args.
+type Builder struct {
+	args *Args
+	errs error
+}
+
+// NewBuilder returns a Builder which will assemble the Args.
+func NewBuilder() *Builder {
+	return &Builder{
+		args: New(),
+	}
+}
+
+// Add inserts a new key/val into the Args being assembled while collecting
+// any errors caused by duplicate keys.
+func (b *Builder) Add(key string, val any) *Builder {
+	b.errs = errors.Join(b.errs, b.args.Add(key, val))
+
+	return b
+}
+
+// Build returns the assembled Args or an error containing a list of
+// errors encountered while trying to build the Args.
+func (b *Builder) Build() (*Args, error) {
+	if b.errs != nil {
+		return nil, b.errs
+	}
+
+	return b.args, nil
+}
+
+// BuildIPLD is the same as Build except it takes the additional step of
+// converting the Args to an ipld.Node.
+func (b *Builder) BuildIPLD() (ipld.Node, error) {
+	args, err := b.Build()
+	if err != nil {
+		return nil, err
+	}
+
+	return args.ToIPLD()
+}
+
+// MustBuild is the same as Build except it panics if an error occurs.
+func (b *Builder) MustBuild() *Args {
+	args, err := b.Build()
+
+	if err != nil {
+		panic(b.errs)
+	}
+
+	return args
+}
+
+// MustBuildIPLD is the same as BuildIPLD except it panics if an error
+// occurs.
+func (b *Builder) MustBuildIPLD() ipld.Node {
+	node, err := b.BuildIPLD()
+	if err != nil {
+		panic(err)
+	}
+
+	return node
+}

pkg/args/builder_test.go

@@ -0,0 +1,82 @@
+package args_test
+
+import (
+	"testing"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/ucan-wg/go-ucan/pkg/args"
+)
+
+func TestBuilder_XXX(t *testing.T) {
+	t.Parallel()
+
+	const (
+		keyOne = "key1"
+		valOne = "string"
+		keyTwo = "key2"
+		valTwo = 42
+	)
+
+	exp := args.New()
+	exp.Add(keyOne, valOne)
+	exp.Add(keyTwo, valTwo)
+
+	expNode, err := exp.ToIPLD()
+	require.NoError(t, err)
+
+	disjointKeys := args.NewBuilder().
+		Add(keyOne, valOne).
+		Add(keyTwo, valTwo)
+
+	duplicateKeys := args.NewBuilder().
+		Add(keyOne, valOne).
+		Add(keyTwo, valTwo).
+		Add(keyOne, "oh no!")
+
+	t.Run("MustBuild succeeds with disjoint keys", func(t *testing.T) {
+		t.Parallel()
+
+		var act *args.Args
+
+		require.NotPanics(t, func() {
+			act = disjointKeys.MustBuild()
+		})
+		assert.Equal(t, exp, act)
+	})
+
+	t.Run("MustBuild fails with duplicate keys", func(t *testing.T) {
+		t.Parallel()
+
+		var act *args.Args
+
+		require.Panics(t, func() {
+			act = duplicateKeys.MustBuild()
+		})
+		assert.Nil(t, act)
+	})
+
+	t.Run("MustBuildIPLD succeeds with disjoint keys", func(t *testing.T) {
+		t.Parallel()
+
+		var act ipld.Node
+
+		require.NotPanics(t, func() {
+			act = disjointKeys.MustBuildIPLD()
+		})
+		assert.Equal(t, expNode, act)
+	})
+
+	t.Run("MustBuildIPLD fails with duplicate keys", func(t *testing.T) {
+		t.Parallel()
+
+		var act ipld.Node
+
+		require.Panics(t, func() {
+			act = duplicateKeys.MustBuildIPLD()
+		})
+		assert.Nil(t, act)
+	})
+}

pkg/args/readonly.go

@@ -0,0 +1,39 @@
+package args
+
+import (
+	"iter"
+
+	"github.com/ipld/go-ipld-prime"
+)
+
+type ReadOnly struct {
+	args *Args
+}
+
+func (r ReadOnly) GetNode(key string) (ipld.Node, error) {
+	return r.args.GetNode(key)
+}
+
+func (r ReadOnly) Len() int {
+	return r.args.Len()
+}
+
+func (r ReadOnly) Iter() iter.Seq2[string, ipld.Node] {
+	return r.args.Iter()
+}
+
+func (r ReadOnly) ToIPLD() (ipld.Node, error) {
+	return r.args.ToIPLD()
+}
+
+func (r ReadOnly) Equals(other ReadOnly) bool {
+	return r.args.Equals(other.args)
+}
+
+func (r ReadOnly) String() string {
+	return r.args.String()
+}
+
+func (r ReadOnly) WriteableClone() *Args {
+	return r.args.Clone()
+}

pkg/claims/claims.go

@@ -0,0 +1,265 @@
+package claims
+
+import (
+	"errors"
+	"fmt"
+	"iter"
+	"sort"
+	"strings"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/printer"
+
+	"github.com/ucan-wg/go-ucan/pkg/policy/literal"
+	"github.com/ucan-wg/go-ucan/pkg/secretbox"
+)
+
+var ErrNotFound = errors.New("key not found in claims")
+
+var ErrNotEncryptable = errors.New("value of this type cannot be encrypted")
+
+// Claims is a container for claims key-value pairs in an attestation token.
+// This also serves as a way to construct the underlying IPLD data with minimum allocations
+// and transformations, while hiding the IPLD complexity from the caller.
+type Claims struct {
+	// This type must be compatible with the IPLD type represented by the IPLD
+	// schema { String : Any }.
+
+	Keys   []string
+	Values map[string]ipld.Node
+}
+
+// NewClaims constructs a new Claims.
+func NewClaims() *Claims {
+	return &Claims{Values: map[string]ipld.Node{}}
+}
+
+// GetBool retrieves a value as a bool.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m *Claims) GetBool(key string) (bool, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return false, ErrNotFound
+	}
+	return v.AsBool()
+}
+
+// GetString retrieves a value as a string.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m *Claims) GetString(key string) (string, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return "", ErrNotFound
+	}
+	return v.AsString()
+}
+
+// GetEncryptedString decorates GetString and decrypt its output with the given symmetric encryption key.
+func (m *Claims) GetEncryptedString(key string, encryptionKey []byte) (string, error) {
+	v, err := m.GetBytes(key)
+	if err != nil {
+		return "", err
+	}
+
+	decrypted, err := secretbox.DecryptStringWithKey(v, encryptionKey)
+	if err != nil {
+		return "", err
+	}
+
+	return string(decrypted), nil
+}
+
+// GetInt64 retrieves a value as an int64.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m *Claims) GetInt64(key string) (int64, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return 0, ErrNotFound
+	}
+	return v.AsInt()
+}
+
+// GetFloat64 retrieves a value as a float64.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m *Claims) GetFloat64(key string) (float64, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return 0, ErrNotFound
+	}
+	return v.AsFloat()
+}
+
+// GetBytes retrieves a value as a []byte.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m *Claims) GetBytes(key string) ([]byte, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return nil, ErrNotFound
+	}
+	return v.AsBytes()
+}
+
+// GetEncryptedBytes decorates GetBytes and decrypt its output with the given symmetric encryption key.
+func (m *Claims) GetEncryptedBytes(key string, encryptionKey []byte) ([]byte, error) {
+	v, err := m.GetBytes(key)
+	if err != nil {
+		return nil, err
+	}
+
+	decrypted, err := secretbox.DecryptStringWithKey(v, encryptionKey)
+	if err != nil {
+		return nil, err
+	}
+
+	return decrypted, nil
+}
+
+// GetNode retrieves a value as a raw IPLD node.
+// Returns ErrNotFound if the given key is missing.
+func (m *Claims) GetNode(key string) (ipld.Node, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return nil, ErrNotFound
+	}
+	return v, nil
+}
+
+// Add adds a key/value pair in the claims set.
+// Accepted types for val are any CBOR compatible type, or directly IPLD values.
+func (m *Claims) Add(key string, val any) error {
+	if _, ok := m.Values[key]; ok {
+		return fmt.Errorf("duplicate key %q", key)
+	}
+
+	node, err := literal.Any(val)
+	if err != nil {
+		return err
+	}
+
+	m.Keys = append(m.Keys, key)
+	m.Values[key] = node
+
+	return nil
+}
+
+// AddEncrypted adds a key/value pair in the claims set.
+// The value is encrypted with the given encryptionKey.
+// Accepted types for the value are: string, []byte.
+// The ciphertext will be 40 bytes larger than the plaintext due to encryption overhead.
+func (m *Claims) AddEncrypted(key string, val any, encryptionKey []byte) error {
+	var encrypted []byte
+	var err error
+
+	switch val := val.(type) {
+	case string:
+		encrypted, err = secretbox.EncryptWithKey([]byte(val), encryptionKey)
+		if err != nil {
+			return err
+		}
+	case []byte:
+		encrypted, err = secretbox.EncryptWithKey(val, encryptionKey)
+		if err != nil {
+			return err
+		}
+	default:
+		return ErrNotEncryptable
+	}
+
+	return m.Add(key, encrypted)
+}
+
+type Iterator interface {
+	Iter() iter.Seq2[string, ipld.Node]
+}
+
+// Include merges the provided claims into the existing one.
+//
+// If duplicate keys are encountered, the new value is silently dropped
+// without causing an error.
+func (m *Claims) Include(other Iterator) {
+	for key, value := range other.Iter() {
+		if _, ok := m.Values[key]; ok {
+			// don't overwrite
+			continue
+		}
+		m.Values[key] = value
+		m.Keys = append(m.Keys, key)
+	}
+}
+
+// Len returns the number of key/values.
+func (m *Claims) Len() int {
+	return len(m.Values)
+}
+
+// Iter iterates over the claims key/values
+func (m *Claims) Iter() iter.Seq2[string, ipld.Node] {
+	return func(yield func(string, ipld.Node) bool) {
+		for _, key := range m.Keys {
+			if !yield(key, m.Values[key]) {
+				return
+			}
+		}
+	}
+}
+
+// Equals tells if two Claims hold the same key/values.
+func (m *Claims) Equals(other *Claims) bool {
+	if len(m.Keys) != len(other.Keys) {
+		return false
+	}
+	if len(m.Values) != len(other.Values) {
+		return false
+	}
+	for _, key := range m.Keys {
+		if !ipld.DeepEqual(m.Values[key], other.Values[key]) {
+			return false
+		}
+	}
+	return true
+}
+
+func (m *Claims) String() string {
+	sort.Strings(m.Keys)
+
+	buf := strings.Builder{}
+	buf.WriteString("{")
+
+	for key, node := range m.Values {
+		buf.WriteString("\n\t")
+		buf.WriteString(key)
+		buf.WriteString(": ")
+		buf.WriteString(strings.ReplaceAll(printer.Sprint(node), "\n", "\n\t"))
+		buf.WriteString(",")
+	}
+
+	if len(m.Values) > 0 {
+		buf.WriteString("\n")
+	}
+	buf.WriteString("}")
+
+	return buf.String()
+}
+
+// ReadOnly returns a read-only version of Claims.
+func (m *Claims) ReadOnly() ReadOnly {
+	return ReadOnly{claims: m}
+}
+
+// Clone makes a deep copy.
+func (m *Claims) Clone() *Claims {
+	res := &Claims{
+		Keys:   make([]string, len(m.Keys)),
+		Values: make(map[string]ipld.Node, len(m.Values)),
+	}
+	copy(res.Keys, m.Keys)
+	for k, v := range m.Values {
+		res.Values[k] = v
+	}
+	return res
+}

pkg/claims/claims_test.go

@@ -0,0 +1,130 @@
+package claims_test
+
+import (
+	"crypto/rand"
+	"maps"
+	"testing"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/node/basicnode"
+	"github.com/stretchr/testify/require"
+
+	"github.com/ucan-wg/go-ucan/pkg/claims"
+)
+
+func TestClaims_Add(t *testing.T) {
+	t.Parallel()
+
+	type Unsupported struct{}
+
+	t.Run("error if not primitive or Node", func(t *testing.T) {
+		t.Parallel()
+
+		err := (&claims.Claims{}).Add("invalid", &Unsupported{})
+		require.Error(t, err)
+	})
+
+	t.Run("encrypted claims", func(t *testing.T) {
+		t.Parallel()
+
+		key := make([]byte, 32)
+		_, err := rand.Read(key)
+		require.NoError(t, err)
+
+		m := claims.NewClaims()
+
+		// string encryption
+		err = m.AddEncrypted("secret", "hello world", key)
+		require.NoError(t, err)
+
+		_, err = m.GetString("secret")
+		require.Error(t, err) // the ciphertext is saved as []byte instead of string
+
+		decrypted, err := m.GetEncryptedString("secret", key)
+		require.NoError(t, err)
+		require.Equal(t, "hello world", decrypted)
+
+		// bytes encryption
+		originalBytes := make([]byte, 128)
+		_, err = rand.Read(originalBytes)
+		require.NoError(t, err)
+		err = m.AddEncrypted("secret-bytes", originalBytes, key)
+		require.NoError(t, err)
+
+		encryptedBytes, err := m.GetBytes("secret-bytes")
+		require.NoError(t, err)
+		require.NotEqual(t, originalBytes, encryptedBytes)
+
+		decryptedBytes, err := m.GetEncryptedBytes("secret-bytes", key)
+		require.NoError(t, err)
+		require.Equal(t, originalBytes, decryptedBytes)
+
+		// error cases
+		t.Run("error on unsupported type", func(t *testing.T) {
+			err := m.AddEncrypted("invalid", 123, key)
+			require.ErrorIs(t, err, claims.ErrNotEncryptable)
+		})
+
+		t.Run("error on invalid key size", func(t *testing.T) {
+			err := m.AddEncrypted("invalid", "test", []byte("short-key"))
+			require.Error(t, err)
+			require.Contains(t, err.Error(), "invalid key size")
+		})
+
+		t.Run("error on nil key", func(t *testing.T) {
+			err := m.AddEncrypted("invalid", "test", nil)
+			require.Error(t, err)
+			require.Contains(t, err.Error(), "encryption key is required")
+		})
+	})
+}
+
+func TestIterCloneEquals(t *testing.T) {
+	m := claims.NewClaims()
+
+	require.NoError(t, m.Add("foo", "bar"))
+	require.NoError(t, m.Add("baz", 1234))
+
+	expected := map[string]ipld.Node{
+		"foo": basicnode.NewString("bar"),
+		"baz": basicnode.NewInt(1234),
+	}
+
+	// claims -> iter
+	require.Equal(t, expected, maps.Collect(m.Iter()))
+
+	// readonly -> iter
+	ro := m.ReadOnly()
+	require.Equal(t, expected, maps.Collect(ro.Iter()))
+
+	// claims -> clone -> iter
+	clone := m.Clone()
+	require.Equal(t, expected, maps.Collect(clone.Iter()))
+
+	// readonly -> WriteableClone -> iter
+	wclone := ro.WriteableClone()
+	require.Equal(t, expected, maps.Collect(wclone.Iter()))
+
+	require.True(t, m.Equals(wclone))
+	require.True(t, ro.Equals(wclone.ReadOnly()))
+}
+
+func TestInclude(t *testing.T) {
+	m1 := claims.NewClaims()
+
+	require.NoError(t, m1.Add("samekey", "bar"))
+	require.NoError(t, m1.Add("baz", 1234))
+
+	m2 := claims.NewClaims()
+
+	require.NoError(t, m2.Add("samekey", "othervalue")) // check no overwrite
+	require.NoError(t, m2.Add("otherkey", 1234))
+
+	m1.Include(m2)
+
+	require.Equal(t, map[string]ipld.Node{
+		"samekey":  basicnode.NewString("bar"),
+		"baz":      basicnode.NewInt(1234),
+		"otherkey": basicnode.NewInt(1234),
+	}, maps.Collect(m1.Iter()))
+}

pkg/claims/readonly.go

@@ -0,0 +1,64 @@
+package claims
+
+import (
+	"iter"
+
+	"github.com/ipld/go-ipld-prime"
+)
+
+// ReadOnly wraps a Claims into a read-only facade.
+type ReadOnly struct {
+	claims *Claims
+}
+
+func (r ReadOnly) GetBool(key string) (bool, error) {
+	return r.claims.GetBool(key)
+}
+
+func (r ReadOnly) GetString(key string) (string, error) {
+	return r.claims.GetString(key)
+}
+
+func (r ReadOnly) GetEncryptedString(key string, encryptionKey []byte) (string, error) {
+	return r.claims.GetEncryptedString(key, encryptionKey)
+}
+
+func (r ReadOnly) GetInt64(key string) (int64, error) {
+	return r.claims.GetInt64(key)
+}
+
+func (r ReadOnly) GetFloat64(key string) (float64, error) {
+	return r.claims.GetFloat64(key)
+}
+
+func (r ReadOnly) GetBytes(key string) ([]byte, error) {
+	return r.claims.GetBytes(key)
+}
+
+func (r ReadOnly) GetEncryptedBytes(key string, encryptionKey []byte) ([]byte, error) {
+	return r.claims.GetEncryptedBytes(key, encryptionKey)
+}
+
+func (r ReadOnly) GetNode(key string) (ipld.Node, error) {
+	return r.claims.GetNode(key)
+}
+
+func (r ReadOnly) Len() int {
+	return r.claims.Len()
+}
+
+func (r ReadOnly) Iter() iter.Seq2[string, ipld.Node] {
+	return r.claims.Iter()
+}
+
+func (r ReadOnly) Equals(other ReadOnly) bool {
+	return r.claims.Equals(other.claims)
+}
+
+func (r ReadOnly) String() string {
+	return r.claims.String()
+}
+
+func (r ReadOnly) WriteableClone() *Claims {
+	return r.claims.Clone()
+}

pkg/command/command.go

@@ -0,0 +1,135 @@
+package command
+
+import (
+	"fmt"
+	"strings"
+)
+
+const separator = "/"
+
+var _ fmt.Stringer = (*Command)(nil)
+
+// Command is a concrete messages (a "verb") that MUST be unambiguously
+// interpretable by the Subject of a UCAN.
+//
+// A [Command] is composed of a leading slash which is optionally followed
+// by one or more slash-separated Segments of lowercase characters.
+//
+// [Command]: https://github.com/ucan-wg/spec#command
+type Command string
+
+// New creates a validated command from the provided list of segment strings.
+// An error is returned if an invalid Command would be formed
+func New(segments ...string) Command {
+	return Top().Join(segments...)
+}
+
+// Parse verifies that the provided string contains the required
+// [segment structure] and, if valid, returns the resulting
+// Command.
+//
+// [segment structure]: https://github.com/ucan-wg/spec#segment-structure
+func Parse(s string) (Command, error) {
+	if !strings.HasPrefix(s, "/") {
+		return "", ErrRequiresLeadingSlash
+	}
+
+	if len(s) > 1 && strings.HasSuffix(s, "/") {
+		return "", ErrDisallowsTrailingSlash
+	}
+
+	if s != strings.ToLower(s) {
+		return "", ErrRequiresLowercase
+	}
+
+	// The leading slash will result in the first element from strings.Split
+	// being an empty string which is removed as strings.Join will ignore it.
+	return Command(s), nil
+}
+
+// MustParse is the same as Parse, but panic() if the parsing fail.
+func MustParse(s string) Command {
+	c, err := Parse(s)
+	if err != nil {
+		panic(err)
+	}
+	return c
+}
+
+// Top is the most powerful capability.
+//
+// This function returns a Command that is a wildcard and therefore represents the
+// most powerful ability. As such, it should be handled with care and used sparingly.
+//
+// [Top]: https://github.com/ucan-wg/spec#-aka-top
+func Top() Command {
+	return Command(separator)
+}
+
+// IsValid returns true if the provided string is a valid UCAN command.
+func IsValid(s string) bool {
+	_, err := Parse(s)
+	return err == nil
+}
+
+// Join appends segments to the end of this command using the required
+// segment separator.
+func (c Command) Join(segments ...string) Command {
+	size := 0
+	for _, s := range segments {
+		size += len(s)
+	}
+	if size == 0 {
+		return c
+	}
+	buf := make([]byte, 0, len(c)+size+len(segments))
+	buf = append(buf, []byte(c)...)
+	for _, s := range segments {
+		if s != "" {
+			if len(buf) > 1 {
+				buf = append(buf, separator...)
+			}
+			buf = append(buf, []byte(s)...)
+		}
+	}
+	return Command(buf)
+}
+
+// Segments returns the ordered segments that comprise the Command as a
+// slice of strings.
+func (c Command) Segments() []string {
+	if c == separator {
+		return nil
+	}
+	return strings.Split(string(c), separator)[1:]
+}
+
+// Covers returns true if the command is identical or a parent of the given other command.
+func (c Command) Covers(other Command) bool {
+	// fast-path, equivalent to the code below (verified with fuzzing)
+	if !strings.HasPrefix(string(other), string(c)) {
+		return false
+	}
+	return c == separator || len(c) == len(other) || other[len(c)] == separator[0]
+
+	/* -------
+
+	otherSegments := other.Segments()
+	if len(otherSegments) < len(c.Segments()) {
+		return false
+	}
+	for i, s := range c.Segments() {
+		if otherSegments[i] != s {
+			return false
+		}
+	}
+	return true
+
+	*/
+}
+
+// String returns the composed representation the command.  This is also
+// the required wire representation (before IPLD encoding occurs.)
+func (c Command) String() string {
+	return string(c)
+}

pkg/command/command_errors.go

@@ -0,0 +1,21 @@
+package command
+
+import "fmt"
+
+// ErrRequiresLeadingSlash is returned when a parsing a string that
+// doesn't start with a [leading slash character].
+//
+// [leading slash character]: https://github.com/ucan-wg/spec#segment-structure
+var ErrRequiresLeadingSlash = fmt.Errorf("a command requires a leading slash character")
+
+// ErrDisallowsTrailingSlash is returned when parsing a string that [ends
+// with a trailing slash character].
+//
+// [ends with a trailing slash character]: https://github.com/ucan-wg/spec#segment-structure
+var ErrDisallowsTrailingSlash = fmt.Errorf("a command must not include a trailing slash")
+
+// ErrRequiresLowercase is returned if a Command contains, or would contain,
+// [uppercase unicode characters].
+//
+// [uppercase unicode characters]: https://github.com/ucan-wg/spec#segment-structure
+var ErrRequiresLowercase = fmt.Errorf("UCAN path segments must must not contain upper-case characters")

pkg/command/command_test.go

@@ -5,7 +5,7 @@ import (
 
 	"github.com/stretchr/testify/require"
 
-	"github.com/ucan-wg/go-ucan/v1/capability/command"
+	"github.com/ucan-wg/go-ucan/pkg/command"
 )
 
 func TestTop(t *testing.T) {
@@ -13,74 +13,81 @@ func TestTop(t *testing.T) {
 }
 
 func TestIsValidCommand(t *testing.T) {
-	t.Parallel()
-
 	t.Run("succeeds when", func(t *testing.T) {
-		t.Parallel()
-
 		for _, testcase := range validTestcases(t) {
-			testcase := testcase
-
 			t.Run(testcase.name, func(t *testing.T) {
-				t.Parallel()
-
 				require.True(t, command.IsValid(testcase.inp))
 			})
 		}
 	})
 
 	t.Run("fails when", func(t *testing.T) {
-		t.Parallel()
-
 		for _, testcase := range invalidTestcases(t) {
-			testcase := testcase
-
 			t.Run(testcase.name, func(t *testing.T) {
-				t.Parallel()
-
 				require.False(t, command.IsValid(testcase.inp))
 			})
 		}
 	})
 }
 
+func TestNew(t *testing.T) {
+	require.Equal(t, command.Top(), command.New())
+	require.Equal(t, "/foo", command.New("foo").String())
+	require.Equal(t, "/foo/bar", command.New("foo", "bar").String())
+	require.Equal(t, "/foo/bar/baz", command.New("foo", "bar/baz").String())
+}
+
 func TestParseCommand(t *testing.T) {
-	t.Parallel()
-
 	t.Run("succeeds when", func(t *testing.T) {
-		t.Parallel()
-
 		for _, testcase := range validTestcases(t) {
-			testcase := testcase
-
 			t.Run(testcase.name, func(t *testing.T) {
-				t.Parallel()
-
 				cmd, err := command.Parse("/elem0/elem1/elem2")
 				require.NoError(t, err)
-				require.NotNil(t, cmd)
+				require.NotEmpty(t, cmd)
 			})
 		}
 	})
 
 	t.Run("fails when", func(t *testing.T) {
-		t.Parallel()
-
 		for _, testcase := range invalidTestcases(t) {
-			testcase := testcase
-
 			t.Run(testcase.name, func(t *testing.T) {
-				t.Parallel()
-
 				cmd, err := command.Parse(testcase.inp)
-				require.ErrorIs(t, err, command.ErrParse)
 				require.ErrorIs(t, err, testcase.err)
-				require.Nil(t, cmd)
+				require.Zero(t, cmd)
 			})
 		}
 	})
 }
 
+func TestEquality(t *testing.T) {
+	require.True(t, command.MustParse("/foo/bar/baz") == command.MustParse("/foo/bar/baz"))
+	require.False(t, command.MustParse("/foo/bar/baz") == command.MustParse("/foo/bar/bazz"))
+	require.False(t, command.MustParse("/foo/bar") == command.MustParse("/foo/bar/baz"))
+}
+
+func TestJoin(t *testing.T) {
+	require.Equal(t, "/foo", command.Top().Join("foo").String())
+	require.Equal(t, "/foo/bar", command.Top().Join("foo/bar").String())
+	require.Equal(t, "/foo/bar", command.Top().Join("foo", "bar").String())
+	require.Equal(t, "/faz/boz/foo/bar", command.MustParse("/faz/boz").Join("foo/bar").String())
+	require.Equal(t, "/faz/boz/foo/bar", command.MustParse("/faz/boz").Join("foo", "bar").String())
+}
+
+func TestSegments(t *testing.T) {
+	require.Empty(t, command.Top().Segments())
+	require.Equal(t, []string{"foo", "bar", "baz"}, command.MustParse("/foo/bar/baz").Segments())
+}
+
+func TestCovers(t *testing.T) {
+	require.True(t, command.MustParse("/foo/bar/baz").Covers(command.MustParse("/foo/bar/baz")))
+	require.True(t, command.MustParse("/foo/bar").Covers(command.MustParse("/foo/bar/baz")))
+	require.False(t, command.MustParse("/foo/bar/baz").Covers(command.MustParse("/foo/bar")))
+	require.True(t, command.MustParse("/").Covers(command.MustParse("/foo")))
+	require.True(t, command.MustParse("/").Covers(command.MustParse("/foo/bar/baz")))
+	require.False(t, command.MustParse("/foo").Covers(command.MustParse("/foo00")))
+	require.False(t, command.MustParse("/foo/bar").Covers(command.MustParse("/foo/bar00")))
+}
+
 type testcase struct {
 	name string
 	inp  string
@@ -134,20 +141,6 @@ func invalidTestcases(t *testing.T) []errorTestcase {
 			},
 			err: command.ErrDisallowsTrailingSlash,
 		},
-		{
-			testcase: testcase{
-				name: "only reserved ucan namespace",
-				inp:  "/ucan",
-			},
-			err: command.ErrUCANNamespaceReserved,
-		},
-		{
-			testcase: testcase{
-				name: "reserved ucan namespace prefix",
-				inp:  "/ucan/elem0/elem1/elem2",
-			},
-			err: command.ErrUCANNamespaceReserved,
-		},
 		{
 			testcase: testcase{
 				name: "uppercase character are present",

pkg/container/Readme.md

@@ -0,0 +1,88 @@
+# Token container
+
+The specification has been promoted to https://github.com/ucan-wg/container.
+
+## Why do I need that?
+
+Some common situation asks to package multiple tokens together:
+- calling a service requires sending an invocation, alongside the matching delegations
+- sending a series of revocations
+- \<insert your application specific scenario here>
+
+The UCAN specification defines how a single token is serialized (envelope with signature, IPLD encoded as Dag-cbor), but it's entirely left open how to package multiple tokens together. To be clear, this is a correct thing to do for a specification, as different ways equally valid to solve that problem exists and can coexist. Any wire format holding a list of bytes would do (cbor, json, csv ...).
+
+**go-ucan** however, provide an opinionated implementation, which may or may not work in your situation. 
+
+Some experiment has been done over which format is appropriate, and two have been selected:
+- **DAG-CBOR** of a list of bytes, as a low overhead option
+- **CAR** file, as a somewhat common ways to cary arbitrary blocks of data
+
+Notably, **compression is not included**, even though it does work reasonably well. This is because your transport medium might already do it, or should.
+
+## Wire format consideration
+
+Several possible formats have been explored:
+- CAR files (binary or base64)
+- DAG-CBOR (binary or base64)
+
+Additionally, gzip and deflate compression has been experimented with.
+
+Below are the results in terms of storage used, as percentage and byte overhead over the raw tokens:
+
+| Token count | car | carBase64 | carGzip | carGzipBase64 | cbor | cborBase64 | cborGzip | cborGzipBase64 | cborFlate | cborFlateBase64 |
+|-------------|-----|-----------|---------|---------------|------|------------|----------|----------------|-----------|-----------------|
+| 1           | 15  | 54        | 7       | 42            | 0    | 35         | \-8      | 22             | \-12      | 16              |
+| 2           | 12  | 49        | \-12    | 15            | 0    | 34         | \-25     | 0              | \-28      | \-3             |
+| 3           | 11  | 48        | \-21    | 4             | 0    | 34         | \-32     | \-10           | \-34      | \-11            |
+| 4           | 10  | 47        | \-26    | \-1           | 0    | 34         | \-36     | \-15           | \-37      | \-17            |
+| 5           | 10  | 47        | \-28    | \-4           | 0    | 34         | \-38     | \-18           | \-40      | \-20            |
+| 6           | 10  | 47        | \-30    | \-7           | 0    | 34         | \-40     | \-20           | \-40      | \-20            |
+| 7           | 10  | 46        | \-31    | \-8           | 0    | 34         | \-41     | \-21           | \-42      | \-22            |
+| 8           | 9   | 46        | \-32    | \-10          | 0    | 34         | \-42     | \-22           | \-42      | \-23            |
+| 9           | 9   | 46        | \-33    | \-11          | 0    | 34         | \-43     | \-23           | \-43      | \-24            |
+| 10          | 9   | 46        | \-34    | \-12          | 0    | 34         | \-43     | \-25           | \-44      | \-25            |
+
+![Overhead %](img/overhead_percent.png)
+
+| Token count | car | carBase64 | carGzip | carGzipBase64 | cbor | cborBase64 | cborGzip | cborGzipBase64 | cborFlate | cborFlateBase64 |
+|-------------|-----|-----------|---------|---------------|------|------------|----------|----------------|-----------|-----------------|
+| 1           | 64  | 226       | 29      | 178           | 4    | 146        | \-35     | 94             | \-52      | 70              |
+| 2           | 102 | 412       | \-107   | 128           | 7    | 288        | \-211    | 0              | \-234     | \-32            |
+| 3           | 140 | 602       | \-270   | 58            | 10   | 430        | \-405    | \-126          | \-429     | \-146           |
+| 4           | 178 | 792       | \-432   | \-28          | 13   | 572        | \-602    | \-252          | \-617     | \-288           |
+| 5           | 216 | 978       | \-582   | \-94          | 16   | 714        | \-805    | \-386          | \-839     | \-418           |
+| 6           | 254 | 1168      | \-759   | \-176         | 19   | 856        | \-1001   | \-508          | \-1018    | \-520           |
+| 7           | 292 | 1358      | \-908   | \-246         | 22   | 998        | \-1204   | \-634          | \-1229    | \-650           |
+| 8           | 330 | 1544      | \-1085  | \-332         | 25   | 1140       | \-1398   | \-756          | \-1423    | \-792           |
+| 9           | 368 | 1734      | \-1257  | \-414         | 28   | 1282       | \-1614   | \-894          | \-1625    | \-930           |
+| 10          | 406 | 1924      | \-1408  | \-508         | 31   | 1424       | \-1804   | \-1040         | \-1826    | \-1060          |
+
+![img.png](img/overhead_bytes.png)
+
+Following is the performance aspect, with CPU usage and memory allocation:
+
+|                 | Write ns/op | Read ns/op | Write B/op | Read B/op | Write allocs/op | Read allocs/op |
+|-----------------|-------------|------------|------------|-----------|-----------------|----------------|
+| car             | 8451        | 1474630    | 17928      | 149437    | 59              | 2631           |
+| carBase64       | 16750       | 1437678    | 24232      | 151502    | 61              | 2633           |
+| carGzip         | 320253      | 1581412    | 823887     | 192272    | 76              | 2665           |
+| carGzipBase64   | 343305      | 1486269    | 828782     | 198543    | 77              | 2669           |
+| cbor            | 6419        | 1301554    | 16368      | 138891    | 25              | 2534           |
+| cborBase64      | 12860       | 1386728    | 20720      | 140962    | 26              | 2536           |
+| cborGzip        | 310106      | 1379146    | 822742     | 182003    | 42              | 2585           |
+| cborGzipBase64  | 317001      | 1462548    | 827640     | 189283    | 43              | 2594           |
+| cborFlate       | 327112      | 1555007    | 822473     | 181537    | 40              | 2591           |
+| cborFlateBase64 | 311276      | 1456562    | 826042     | 188665    | 41              | 2596           |
+
+(BEWARE: logarithmic scale)
+
+![img.png](img/cpu.png)
+![img_1.png](img/alloc_byte.png)
+![img_2.png](img/alloc_count.png)
+
+Conclusion:
+- CAR files are heavy for this usage, notably because they carry the CIDs of the tokens
+- compression works quite well and warrants its usage even with a single token
+- DAG-CBOR outperform CAR files everywhere, and comes with a tiny ~3 bytes per token overhead.
+
+**Formats beside DAG-CBOR and CAR, with or without base64, have been removed. They are in the git history though.**

pkg/container/car.go

@@ -0,0 +1,263 @@
+package container
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"io"
+	"iter"
+
+	"github.com/ipfs/go-cid"
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/codec/dagcbor"
+	"github.com/ipld/go-ipld-prime/datamodel"
+	"github.com/ipld/go-ipld-prime/fluent/qp"
+	cidlink "github.com/ipld/go-ipld-prime/linking/cid"
+	"github.com/ipld/go-ipld-prime/node/basicnode"
+)
+
+/*
+	Note: below is essentially a re-implementation of the CAR file v1 read and write.
+	This exists here for two reasons:
+		- go-car's API forces to go through an IPLD getter or through a blockstore API
+		- generally, go-car is a very complex and large dependency
+*/
+
+// EmptyCid is a "zero" Cid: zero-length "identity" multihash with "raw" codec
+// It can be used to have at least one root in a CARv1 file (making it legal), yet
+// denote that it can be ignored.
+var EmptyCid = cid.MustParse([]byte{01, 55, 00, 00})
+
+type carBlock struct {
+	c    cid.Cid
+	data []byte
+}
+
+// writeCar writes a CARv1 file containing the blocks from the iterator.
+// If no roots are provided, a single EmptyCid is used as root to make the file
+// spec compliant.
+func writeCar(w io.Writer, roots []cid.Cid, blocks iter.Seq2[carBlock, error]) error {
+	if len(roots) == 0 {
+		roots = []cid.Cid{EmptyCid}
+	}
+	h := carHeader{
+		Roots:   roots,
+		Version: 1,
+	}
+	hb, err := h.Write()
+	if err != nil {
+		return err
+	}
+	err = ldWrite(w, hb)
+	if err != nil {
+		return err
+	}
+
+	for block, err := range blocks {
+		if err != nil {
+			return err
+		}
+		err = ldWrite(w, block.c.Bytes(), block.data)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// readCar reads a CARv1 file from the reader, and return a block iterator.
+// Roots are ignored.
+func readCar(r io.Reader) (roots []cid.Cid, blocks iter.Seq2[carBlock, error], err error) {
+	br := bufio.NewReader(r)
+
+	hb, err := ldRead(br)
+	if err != nil {
+		return nil, nil, err
+	}
+	h, err := readHeader(hb)
+	if err != nil {
+		return nil, nil, err
+	}
+	if h.Version != 1 {
+		return nil, nil, fmt.Errorf("invalid car version: %d", h.Version)
+	}
+
+	return h.Roots, func(yield func(block carBlock, err error) bool) {
+		for {
+			block, err := readBlock(br)
+			if err == io.EOF {
+				return
+			}
+			if err != nil {
+				if !yield(carBlock{}, err) {
+					return
+				}
+			}
+			if !yield(block, nil) {
+				return
+			}
+		}
+	}, nil
+}
+
+// readBlock reads a section from the reader and decode a (cid+data) block.
+func readBlock(r *bufio.Reader) (carBlock, error) {
+	raw, err := ldRead(r)
+	if err != nil {
+		return carBlock{}, err
+	}
+
+	n, c, err := cid.CidFromReader(bytes.NewReader(raw))
+	if err != nil {
+		return carBlock{}, err
+	}
+	data := raw[n:]
+
+	// integrity check
+	hashed, err := c.Prefix().Sum(data)
+	if err != nil {
+		return carBlock{}, err
+	}
+
+	if !hashed.Equals(c) {
+		return carBlock{}, fmt.Errorf("mismatch in content integrity, name: %s, data: %s", c, hashed)
+	}
+
+	return carBlock{c: c, data: data}, nil
+}
+
+// maxAllowedSectionSize dictates the maximum number of bytes that a CARv1 header
+// or section is allowed to occupy without causing a decode to error.
+// This cannot be supplied as an option, only adjusted as a global. You should
+// use v2#NewReader instead since it allows for options to be passed in.
+var maxAllowedSectionSize uint = 32 << 20 // 32MiB
+
+// ldRead performs a length-delimited read of a section from the reader.
+// A section is composed of an uint length followed by the data.
+func ldRead(r *bufio.Reader) ([]byte, error) {
+	if _, err := r.Peek(1); err != nil { // no more blocks, likely clean io.EOF
+		return nil, err
+	}
+
+	l, err := binary.ReadUvarint(r)
+	if err != nil {
+		if err == io.EOF {
+			return nil, io.ErrUnexpectedEOF // don't silently pretend this is a clean EOF
+		}
+		return nil, err
+	}
+	if l == 0 {
+		return nil, fmt.Errorf("invalid zero size section")
+	}
+
+	if l > uint64(maxAllowedSectionSize) { // Don't OOM
+		return nil, fmt.Errorf("malformed car; header is bigger than MaxAllowedSectionSize")
+	}
+
+	buf := make([]byte, l)
+	if _, err := io.ReadFull(r, buf); err != nil {
+		if err == io.EOF {
+			// we should be able to read the promised bytes, this is not normal
+			return nil, io.ErrUnexpectedEOF
+		}
+		return nil, err
+	}
+
+	return buf, nil
+}
+
+// ldWrite performs a length-delimited write of a section on the writer.
+// A section is composed of an uint length followed by the data.
+func ldWrite(w io.Writer, d ...[]byte) error {
+	var sum uint64
+	for _, s := range d {
+		sum += uint64(len(s))
+	}
+
+	buf := make([]byte, 8)
+	n := binary.PutUvarint(buf, sum)
+	_, err := w.Write(buf[:n])
+	if err != nil {
+		return err
+	}
+
+	for _, s := range d {
+		_, err = w.Write(s)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+type carHeader struct {
+	Roots   []cid.Cid
+	Version uint64
+}
+
+const rootsKey = "roots"
+const versionKey = "version"
+
+func readHeader(data []byte) (*carHeader, error) {
+	var header carHeader
+
+	nd, err := ipld.Decode(data, dagcbor.Decode)
+	if err != nil {
+		return nil, err
+	}
+	if nd.Length() != 2 {
+		return nil, fmt.Errorf("malformed car header")
+	}
+	rootsNd, err := nd.LookupByString(rootsKey)
+	if err != nil {
+		return nil, fmt.Errorf("malformed car header")
+	}
+	it := rootsNd.ListIterator()
+	if it == nil {
+		return nil, fmt.Errorf("malformed car header")
+	}
+	header.Roots = make([]cid.Cid, 0, rootsNd.Length())
+	for !it.Done() {
+		_, nd, err := it.Next()
+		if err != nil {
+			return nil, err
+		}
+		lk, err := nd.AsLink()
+		if err != nil {
+			return nil, err
+		}
+		switch lk := lk.(type) {
+		case cidlink.Link:
+			header.Roots = append(header.Roots, lk.Cid)
+		default:
+			return nil, fmt.Errorf("malformed car header")
+		}
+	}
+	versionNd, err := nd.LookupByString(versionKey)
+	if err != nil {
+		return nil, fmt.Errorf("malformed car header")
+	}
+	version, err := versionNd.AsInt()
+	if err != nil {
+		return nil, fmt.Errorf("malformed car header")
+	}
+	header.Version = uint64(version)
+	return &header, nil
+}
+
+func (ch *carHeader) Write() ([]byte, error) {
+	nd, err := qp.BuildMap(basicnode.Prototype.Any, 2, func(ma datamodel.MapAssembler) {
+		qp.MapEntry(ma, rootsKey, qp.List(int64(len(ch.Roots)), func(la datamodel.ListAssembler) {
+			for _, root := range ch.Roots {
+				qp.ListEntry(la, qp.Link(cidlink.Link{Cid: root}))
+			}
+		}))
+		qp.MapEntry(ma, versionKey, qp.Int(1))
+	})
+	if err != nil {
+		return nil, err
+	}
+	return ipld.Encode(nd, dagcbor.Encode)
+}

pkg/container/car_test.go

@@ -0,0 +1,85 @@
+package container
+
+import (
+	"bytes"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestCarRoundTrip(t *testing.T) {
+	// this car file is a complex and legal CARv1 file
+	original, err := os.ReadFile("testdata/sample-v1.car")
+	require.NoError(t, err)
+
+	roots, it, err := readCar(bytes.NewReader(original))
+	require.NoError(t, err)
+
+	var blks []carBlock
+	for blk, err := range it {
+		require.NoError(t, err)
+		blks = append(blks, blk)
+	}
+
+	require.Len(t, blks, 1049)
+
+	buf := bytes.NewBuffer(nil)
+
+	err = writeCar(buf, roots, func(yield func(carBlock, error) bool) {
+		for _, blk := range blks {
+			if !yield(blk, nil) {
+				return
+			}
+		}
+	})
+	require.NoError(t, err)
+
+	// Bytes equal after the round-trip
+	require.Equal(t, original, buf.Bytes())
+}
+
+func FuzzCarRoundTrip(f *testing.F) {
+	// Note: this fuzzing is somewhat broken.
+	// After some time, the fuzzer discover that a varint can be serialized in different
+	// ways that lead to the same integer value. This means that the CAR format can have
+	// multiple legal binary representation for the exact same data, which is what we are
+	// trying to detect here. Ideally, the format would be stricter, but that's how things
+	// are.
+
+	example, err := os.ReadFile("testdata/sample-v1.car")
+	require.NoError(f, err)
+
+	f.Add(example)
+
+	f.Fuzz(func(t *testing.T, data []byte) {
+		roots, blocksIter, err := readCar(bytes.NewReader(data))
+		if err != nil {
+			// skip invalid binary
+			t.Skip()
+		}
+
+		// reading all the blocks, which force reading and verifying the full file
+		var blocks []carBlock
+		for block, err := range blocksIter {
+			if err != nil {
+				// error reading, invalid data
+				t.Skip()
+			}
+			blocks = append(blocks, block)
+		}
+
+		var buf bytes.Buffer
+		err = writeCar(&buf, roots, func(yield func(carBlock, error) bool) {
+			for _, blk := range blocks {
+				if !yield(blk, nil) {
+					return
+				}
+			}
+		})
+		require.NoError(t, err)
+
+		// test if the round-trip produce a byte-equal CAR
+		require.Equal(t, data, buf.Bytes())
+	})
+}

pkg/container/containertest/Base64StdPaddingGzipped

@@ -0,0 +1 @@
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

pkg/container/containertest/Base64URLGzipped

@@ -0,0 +1 @@
+PH4sIAAAAAAAA_5zW65MU1f3HcS7-hB8igpfIgqUxCqLC0tfTfUADMzs7M87ObubaOzMEsM-lp6eb6Zmee49GvEKwVBQRgygIUVHLCwoqoJAAikCQaJRICCqFGPCCcXVFoaBMJbukKs929h94P3nV-ZzvSg2XrEkV9u7kwFW3J6bv7bj7tflfrjm4e8_grc7Dke4jPx6c_Mm87olH_O9Of35_59-X7z2xe056dKx7156F074aOXzCcemCRe-Y4T3n3v7SNV-fdd4qVfcLA48NPDbwArtYxqo1mcxJT2ebmWZmUgE3s09jtUxqMsmQKSZ1ptRBu5lF0WK75ZbawpVO25NW2rLtfgG5XFZKtlwBr1GPVfyKU9YjZS_BOEv0yVouNxmpBUxr-TH6osmv4Uyx-L9NM5PUWqLtmqTohbQnkWp1i5JlxiOWLxAFAdaJeU13Z0gwWsN2AOdzc267A6tz5uDmGTPvUH-pNVfUOWU6CBfLqP9ZkqUl9fc6w3KqRmTVUDWGB1BiiKoDCBhJptRABAuCxrJY0zHPQBZjbLCY8hKCVBOplbMwDXbdsO9O4ZT5m20fTPywBymh3HfTBjDl5MzlT65xpm15kC4-f_2hlTtKyQUbrj78wBPfjn1e3T9i7OmuEfmt25d4z_q2K_0H36lRiw_9NbK0Szy0d3A_kPKuFk6qOYqVTSCj2uGNknxdT0BN0Etlqklxr8QaSqzF468oQl-R0oo7rztKQaK5crqzmMq7vOV4uh4jFZ2zPIrfFL0hS_ZYOFikDSA1ku1FAqJEZIRUA2gMy0OeY4EOKGVlHmCDIgZKKhYhp2NKGQR5YvBYZAWVp4j0Io1b4N905xU_e_SJj1-4pAfpbefa207fnMit_9XP39xxw7D3Fk0bH7vs09W_3uwcG3Vk5Nxv14yYP2Zj7lLPQ01Nnw0bsmXTssuZprL6-dX3zB3U9NH9q8_tB1KhgwUG8gA54HH5OcMyW1vqjmLnO11GNB0Ph6ut8WI1zAbdSMv2FclKhWK2riCS9trFvDvmd3tC0bpo8SAeC5QExZfiO3LeIOuKePkGkBrJnkEiWJYlnjEg1nhERSKouowIUgEvGUTGRBN5Ims6QiyVZVUwNIp4GUNOxr1I199x4OH_y6103Q-3DOhBuhYw1x1Y9eHYjejREfahp2Z9SNaqo83Xb0yff-mFr3_srFg7at3FV2aEy28atv2p8zbc-313YOQ3y65gm1Z9MHzdipHm0H4gFYmaLrQGWjpFLp4ICmagamWKHI560tlAsoa1uNcotoQKWj7fGuvz3Ck1v5hJgvZQJGYIKTlcFrypWocVLHPuEC_oWa2e0M3OVsen-BuZuwayZ-YOckQARDJ4TLAsChqUdVHVOBkA1pA5GVKGkaiqA04CDISiIcoUMhRjCHuRmjJraxO7f_ji-PiTE3pf0g83F4Zc-hF4-7uTV4XPG7xw986TC__2_qlnjrf9OLDrrKfeXioPGvtN0-NHRv8OHh7_5fzP1V3Lt40Zar-z-c3Vtx5O54b0AykTCrGsVS1iKmkdapQ1q6lqKWkV2gD1J3MIY09SlHw5O6yHgn1FqnoTLU66YobsbASoKq46rmoka2c8LomNkHBFYH2VVldNa-GTQgNIjWR7kTiVAIYRsYEFTcMCgpDqogw4TFXGwKqmYaACRtMJ4ClmEDAQFaHAYAbSXqRXxt9z8fIVxXOXjpjI9SDtXIkK6MJ3T6xbv-WuN7azi9K8UGl5a1t056x9G6fgxJJ5g03lSBk_O2juXV0Lnh2kVHfIwcqrKw-9dboId5X-eU5__iRPLhyxMsF03C9ZnWYKtRfZajIbUDjb68k7XFG2UL5adKesKOwrku42qkgrRaK2lI1jYJaMelnpaLf9RhW0sfmUrjk-FymaAcHBDSA1ku1FYjVeBBpGBqUCpjIUKdI5TuAwwqqhiQAAyvAQ6BoDBCgiwSCizMsSQhzfi_SP-2K_-PGE9saxTzMze5Dy-z0P7Di679olRys3fzdIXbZgbpvy0Krm5oXnnP_1w9yzj0yF8_64bCjzW2H22feEv48NLk6_8UD32fWPNvlf_CS18OUB_UDSE1WcaNUKSsqx_SjA-zNeLYI4T0cybfM4pbMg4AknnbbOetjqK1K-blcKUt4DWcNrVBzBIiJ2fGE7W8gCKZbI4WhBy4KkP9MWhA0gNZL9LxJLVMQhA_KEkTAjEkbnBZFILMQGQRLPi5gSpAOqEShqqoFFWZA4jCHoRRLeO9XcMqtwy7p35cd6kIY99snirRBtnvqcHN9benz4hCuG3LJt9bafZki7thTP_mHpi5PGXfbY6N1Nm68Z992tLD51S-q5DR98dsnhAbNSNzwZvOr_-4FUTdpy0XIjlg0nZSHkqaneUBVUCylgZEtmwQ3LhZrhR3WtkrX7PHegSpISVKtKuCYFyu11s5pK6FHbR112BNtsIZUOt1fSHVIuLzYydw1kz8ydoGqUF4nBizIHZYFyog5ZLHCU0QwEOZGROVEiusr824blDCgBSSIMgGdO8ClPP7KYPJnsQIeKG3uQrnz5teFvvD98hrrOc3nrmK3rn9s_-09PjBzaddOwxDl3Hz1xfEx810uPhvYcbL3sL9dNWjnuxamjXnCFEheAP29i5nXf3tGf6y7r6qwrJZfHlLyGLCvuWCf05Qp6JGDYBaNWqnvS5bKN_VRBVaWvSDnJBG4lHBEAl05yIccVIHZabmmLBttdobSjaKY3FRY9alvY42oAqZFsL5KKCAaEQkMlokgpyzKijhlRpaIoGZClCLCU1ahOIGQhFWSDQwLLqkhlzrwkvOH-ScEtSw68Omr87B6kpYWRa185WbvuC8u8aMC0i1pXbHeO72P9982fsHhh2xbf8WGe0y5Zq-wAk3YenZ05evG93MzVAx78aXJlxr1r2hce7A9Srqh6jIIVjNU7INENUg7Tqmz7tFBb2pfy-oq6zxuOOO0kWo27-3yC58tCwi900DxOtpk-k2txFCfuCGKllnOscqVk-W0N1dmoFcw3coI3kO1FElVWYhiiGhzgCS-xPES6zFKVAZxgyIAXJZWjAOsygppAEG_8Z-wIQZzai7Ri5eyp3V8981nL9fET_woAAP__svLMp3sQAAA

pkg/container/containertest/containertest.go

@@ -0,0 +1,21 @@
+package containertest
+
+import _ "embed"
+
+//go:embed Base64StdPadding
+var Base64StdPadding string
+
+//go:embed Base64StdPaddingGzipped
+var Base64StdPaddingGzipped string
+
+//go:embed Base64URL
+var Base64URL string
+
+//go:embed Base64URLGzipped
+var Base64URLGzipped string
+
+//go:embed Bytes
+var Bytes []byte
+
+//go:embed BytesGzipped
+var BytesGzipped []byte

pkg/container/packaging.go

@@ -0,0 +1,118 @@
+package container
+
+import (
+	"compress/gzip"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+)
+
+const containerVersionTag = "ctn-v1"
+
+type header byte
+
+const (
+	headerRawBytes             = header(0x40)
+	headerBase64StdPadding     = header(0x42)
+	headerBase64URL            = header(0x43)
+	headerRawBytesGzip         = header(0x4D)
+	headerBase64StdPaddingGzip = header(0x4F)
+	headerBase64URLGzip        = header(0x50)
+)
+
+func (h header) encoder(w io.Writer) *payloadWriter {
+	res := &payloadWriter{rawWriter: w, writer: w, header: h}
+
+	switch h {
+	case headerBase64StdPadding, headerBase64StdPaddingGzip:
+		b64Writer := base64.NewEncoder(base64.StdEncoding, res.writer)
+		res.writer = b64Writer
+		res.closers = append([]io.Closer{b64Writer}, res.closers...)
+	case headerBase64URL, headerBase64URLGzip:
+		b64Writer := base64.NewEncoder(base64.RawURLEncoding, res.writer)
+		res.writer = b64Writer
+		res.closers = append([]io.Closer{b64Writer}, res.closers...)
+	}
+
+	switch h {
+	case headerRawBytesGzip, headerBase64StdPaddingGzip, headerBase64URLGzip:
+		gzipWriter := gzip.NewWriter(res.writer)
+		res.writer = gzipWriter
+		res.closers = append([]io.Closer{gzipWriter}, res.closers...)
+	}
+
+	return res
+}
+
+func payloadDecoder(r io.Reader) (io.Reader, error) {
+	headerBuf := make([]byte, 1)
+	_, err := r.Read(headerBuf)
+	if err != nil {
+		return nil, err
+	}
+	h := header(headerBuf[0])
+
+	switch h {
+	case headerRawBytes,
+		headerBase64StdPadding,
+		headerBase64URL,
+		headerRawBytesGzip,
+		headerBase64StdPaddingGzip,
+		headerBase64URLGzip:
+	default:
+		return nil, fmt.Errorf("unknown container header")
+	}
+
+	switch h {
+	case headerBase64StdPadding, headerBase64StdPaddingGzip:
+		r = base64.NewDecoder(base64.StdEncoding, r)
+	case headerBase64URL, headerBase64URLGzip:
+		r = base64.NewDecoder(base64.RawURLEncoding, r)
+	}
+
+	switch h {
+	case headerRawBytesGzip, headerBase64StdPaddingGzip, headerBase64URLGzip:
+		gzipReader, err := gzip.NewReader(r)
+		if err != nil {
+			return nil, err
+		}
+		r = gzipReader
+	}
+
+	return r, nil
+}
+
+var _ io.WriteCloser = &payloadWriter{}
+
+// payloadWriter is tasked with two things:
+// - prepend the header byte
+// - call Close() on all the underlying io.Writer
+type payloadWriter struct {
+	rawWriter   io.Writer
+	writer      io.Writer
+	header      header
+	headerWrote bool
+	closers     []io.Closer
+}
+
+func (w *payloadWriter) Write(p []byte) (n int, err error) {
+	if !w.headerWrote {
+		_, err := w.rawWriter.Write([]byte{byte(w.header)})
+		if err != nil {
+			return 0, err
+		}
+		w.headerWrote = true
+	}
+	return w.writer.Write(p)
+}
+
+func (w *payloadWriter) Close() error {
+	var errs error
+	for _, closer := range w.closers {
+		if err := closer.Close(); err != nil {
+			errs = errors.Join(errs, err)
+		}
+	}
+	return errs
+}

pkg/container/reader.go

@@ -0,0 +1,235 @@
+package container
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"iter"
+	"strings"
+
+	"github.com/ipfs/go-cid"
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/codec/cbor"
+	"github.com/ipld/go-ipld-prime/datamodel"
+
+	"github.com/ucan-wg/go-ucan/token"
+	"github.com/ucan-wg/go-ucan/token/delegation"
+	"github.com/ucan-wg/go-ucan/token/invocation"
+)
+
+var ErrNotFound = fmt.Errorf("not found")
+var ErrMultipleInvocations = fmt.Errorf("multiple invocations")
+
+// Reader is a token container reader. It exposes the tokens conveniently decoded.
+type Reader map[cid.Cid]bundle
+
+type bundle struct {
+	sealed []byte
+	token  token.Token
+}
+
+// FromBytes decodes a container from a []byte
+func FromBytes(data []byte) (Reader, error) {
+	return FromReader(bytes.NewReader(data))
+}
+
+// FromString decodes a container from a string
+func FromString(s string) (Reader, error) {
+	return FromReader(strings.NewReader(s))
+}
+
+// FromReader decodes a container from an io.Reader.
+func FromReader(r io.Reader) (Reader, error) {
+	payload, err := payloadDecoder(r)
+	if err != nil {
+		return nil, err
+	}
+
+	n, err := ipld.DecodeStreaming(payload, cbor.Decode)
+	if err != nil {
+		return nil, err
+	}
+	if n.Kind() != datamodel.Kind_Map {
+		return nil, fmt.Errorf("invalid container format: expected map")
+	}
+	if n.Length() != 1 {
+		return nil, fmt.Errorf("invalid container format: expected single version key")
+	}
+
+	// get the first (and only) key-value pair
+	it := n.MapIterator()
+	key, tokensNode, err := it.Next()
+	if err != nil {
+		return nil, err
+	}
+
+	version, err := key.AsString()
+	if err != nil {
+		return nil, fmt.Errorf("invalid container format: version must be string")
+	}
+	if version != containerVersionTag {
+		return nil, fmt.Errorf("unsupported container version: %s", version)
+	}
+
+	if tokensNode.Kind() != datamodel.Kind_List {
+		return nil, fmt.Errorf("invalid container format: tokens must be a list")
+	}
+
+	ctn := make(Reader, tokensNode.Length())
+	it2 := tokensNode.ListIterator()
+	for !it2.Done() {
+		_, val, err := it2.Next()
+		if err != nil {
+			return nil, err
+		}
+		data, err := val.AsBytes()
+		if err != nil {
+			return nil, err
+		}
+		err = ctn.addToken(data)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return ctn, nil
+}
+
+// GetToken returns an arbitrary decoded token, from its CID.
+// If not found, ErrNotFound is returned.
+func (ctn Reader) GetToken(cid cid.Cid) (token.Token, error) {
+	bndl, ok := ctn[cid]
+	if !ok {
+		return nil, ErrNotFound
+	}
+	return bndl.token, nil
+}
+
+// GetSealed returns an arbitrary sealed token, from its CID.
+// If not found, ErrNotFound is returned.
+func (ctn Reader) GetSealed(cid cid.Cid) ([]byte, error) {
+	bndl, ok := ctn[cid]
+	if !ok {
+		return nil, ErrNotFound
+	}
+	return bndl.sealed, nil
+}
+
+// GetAllTokens return all the tokens in the container.
+func (ctn Reader) GetAllTokens() iter.Seq[token.Bundle] {
+	return func(yield func(token.Bundle) bool) {
+		for c, bndl := range ctn {
+			if !yield(token.Bundle{
+				Cid:     c,
+				Decoded: bndl.token,
+				Sealed:  bndl.sealed,
+			}) {
+				return
+			}
+		}
+	}
+}
+
+// GetDelegation is the same as GetToken but only return a delegation.Token, with the right type.
+// If not found, delegation.ErrDelegationNotFound is returned.
+func (ctn Reader) GetDelegation(cid cid.Cid) (*delegation.Token, error) {
+	tkn, err := ctn.GetToken(cid)
+	if err != nil { // only ErrNotFound expected
+		return nil, delegation.ErrDelegationNotFound
+	}
+	if tkn, ok := tkn.(*delegation.Token); ok {
+		return tkn, nil
+	}
+	return nil, delegation.ErrDelegationNotFound
+}
+
+// GetDelegationBundle is the same as GetToken but only return a delegation.Bundle, with the right type.
+// If not found, delegation.ErrDelegationNotFound is returned.
+func (ctn Reader) GetDelegationBundle(cid cid.Cid) (*delegation.Bundle, error) {
+	bndl, ok := ctn[cid]
+	if !ok {
+		return nil, delegation.ErrDelegationNotFound
+	}
+	if tkn, ok := bndl.token.(*delegation.Token); ok {
+		return &delegation.Bundle{
+			Cid:     cid,
+			Decoded: tkn,
+			Sealed:  bndl.sealed,
+		}, nil
+	}
+	return nil, delegation.ErrDelegationNotFound
+}
+
+// GetAllDelegations returns all the delegation.Token in the container.
+func (ctn Reader) GetAllDelegations() iter.Seq[*delegation.Bundle] {
+	return func(yield func(*delegation.Bundle) bool) {
+		for c, bndl := range ctn {
+			if t, ok := bndl.token.(*delegation.Token); ok {
+				if !yield(&delegation.Bundle{
+					Cid:     c,
+					Decoded: t,
+					Sealed:  bndl.sealed,
+				}) {
+					return
+				}
+			}
+		}
+	}
+}
+
+// GetInvocation returns a single invocation.Token.
+// If none are found, ErrNotFound is returned.
+// If more than one invocation exists, ErrMultipleInvocations is returned.
+func (ctn Reader) GetInvocation() (*invocation.Token, error) {
+	var res *invocation.Token
+	for _, bndl := range ctn {
+		if inv, ok := bndl.token.(*invocation.Token); ok {
+			if res != nil {
+				return nil, ErrMultipleInvocations
+			}
+			res = inv
+		}
+	}
+	if res == nil {
+		return nil, ErrNotFound
+	}
+	return res, nil
+}
+
+// GetAllInvocations returns all the invocation.Token in the container.
+func (ctn Reader) GetAllInvocations() iter.Seq[invocation.Bundle] {
+	return func(yield func(invocation.Bundle) bool) {
+		for c, bndl := range ctn {
+			if t, ok := bndl.token.(*invocation.Token); ok {
+				if !yield(invocation.Bundle{
+					Cid:     c,
+					Decoded: t,
+					Sealed:  bndl.sealed,
+				}) {
+					return
+				}
+			}
+		}
+	}
+}
+
+func (ctn Reader) addToken(data []byte) error {
+	tkn, c, err := token.FromSealed(data)
+	if err != nil {
+		return err
+	}
+	ctn[c] = bundle{
+		sealed: data,
+		token:  tkn,
+	}
+	return nil
+}
+
+// ToWriter convert a container Reader into a Writer.
+// Most likely, you only want to use this in tests for convenience.
+func (ctn Reader) ToWriter() Writer {
+	writer := NewWriter()
+	for _, bndl := range ctn {
+		writer.AddSealed(bndl.sealed)
+	}
+	return writer
+}

pkg/container/serial_test.go

@@ -0,0 +1,243 @@
+package container
+
+import (
+	"bytes"
+	"crypto/rand"
+	"fmt"
+	"io"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/MetaMask/go-did-it"
+	"github.com/MetaMask/go-did-it/controller/did-key"
+	"github.com/MetaMask/go-did-it/crypto/ed25519"
+	"github.com/ipfs/go-cid"
+	"github.com/stretchr/testify/require"
+
+	"github.com/ucan-wg/go-ucan/pkg/command"
+	"github.com/ucan-wg/go-ucan/pkg/policy"
+	"github.com/ucan-wg/go-ucan/pkg/policy/literal"
+	"github.com/ucan-wg/go-ucan/token/delegation"
+)
+
+func TestContainerRoundTrip(t *testing.T) {
+	for _, tc := range []struct {
+		name           string
+		expectedHeader header
+		writer         any
+	}{
+		{"Bytes", headerRawBytes, Writer.ToBytes},
+		{"BytesWriter", headerRawBytes, Writer.ToBytesWriter},
+		{"BytesGzipped", headerRawBytesGzip, Writer.ToBytesGzipped},
+		{"BytesGzippedWriter", headerRawBytesGzip, Writer.ToBytesGzippedWriter},
+		{"Base64StdPadding", headerBase64StdPadding, Writer.ToBase64StdPadding},
+		{"Base64StdPaddingWriter", headerBase64StdPadding, Writer.ToBase64StdPaddingWriter},
+		{"Base64StdPaddingGzipped", headerBase64StdPaddingGzip, Writer.ToBase64StdPaddingGzipped},
+		{"Base64StdPaddingGzippedWriter", headerBase64StdPaddingGzip, Writer.ToBase64StdPaddingGzippedWriter},
+		{"Base64URL", headerBase64URL, Writer.ToBase64URL},
+		{"Base64URLWriter", headerBase64URL, Writer.ToBase64URLWriter},
+		{"Base64URLGzipped", headerBase64URLGzip, Writer.ToBase64URLGzipped},
+		{"Base64URLGzipWriter", headerBase64URLGzip, Writer.ToBase64URLGzipWriter},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			tokens := make(map[cid.Cid]*delegation.Token)
+			var dataSize int
+
+			writer := NewWriter()
+
+			for i := 0; i < 10; i++ {
+				dlg, c, data := randToken()
+				writer.AddSealed(data)
+				tokens[c] = dlg
+				dataSize += len(data)
+			}
+
+			var reader Reader
+			var serialLen int
+
+			switch fn := tc.writer.(type) {
+			case func(ctn Writer, w io.Writer) error:
+				buf := bytes.NewBuffer(nil)
+				err := fn(writer, buf)
+				require.NoError(t, err)
+				serialLen = buf.Len()
+
+				h, err := buf.ReadByte()
+				require.NoError(t, err)
+				require.Equal(t, byte(tc.expectedHeader), h)
+				err = buf.UnreadByte()
+				require.NoError(t, err)
+
+				reader, err = FromReader(bytes.NewReader(buf.Bytes()))
+				require.NoError(t, err)
+
+			case func(ctn Writer) ([]byte, error):
+				b, err := fn(writer)
+				require.NoError(t, err)
+				serialLen = len(b)
+
+				require.Equal(t, byte(tc.expectedHeader), b[0])
+
+				reader, err = FromBytes(b)
+				require.NoError(t, err)
+
+			case func(ctn Writer) (string, error):
+				s, err := fn(writer)
+				require.NoError(t, err)
+				serialLen = len(s)
+
+				require.Equal(t, byte(tc.expectedHeader), s[0])
+
+				reader, err = FromString(s)
+				require.NoError(t, err)
+			}
+
+			t.Logf("data size %d, container size %d, overhead: %d%%, %d bytes",
+				dataSize, serialLen, int(float32(serialLen-dataSize)/float32(dataSize)*100.0), serialLen-dataSize)
+
+			for c, dlg := range tokens {
+				tknRead, err := reader.GetToken(c)
+				require.NoError(t, err)
+
+				// require.Equal fails as time.Time holds a wall time that is going to be
+				// different, even if it represents the same event.
+				// We need to do the following instead.
+
+				dlgRead := tknRead.(*delegation.Token)
+				require.Equal(t, dlg.Issuer(), dlgRead.Issuer())
+				require.Equal(t, dlg.Audience(), dlgRead.Audience())
+				require.Equal(t, dlg.Subject(), dlgRead.Subject())
+				require.Equal(t, dlg.Command(), dlgRead.Command())
+				require.Equal(t, dlg.Policy(), dlgRead.Policy())
+				require.Equal(t, dlg.Nonce(), dlgRead.Nonce())
+				require.True(t, dlg.Meta().Equals(dlgRead.Meta()))
+				if dlg.NotBefore() != nil {
+					// within 1s as the original value gets truncated to seconds when serialized
+					require.WithinDuration(t, *dlg.NotBefore(), *dlgRead.NotBefore(), time.Second)
+				}
+				if dlg.Expiration() != nil {
+					// within 1s as the original value gets truncated to seconds when serialized
+					require.WithinDuration(t, *dlg.Expiration(), *dlgRead.Expiration(), time.Second)
+				}
+			}
+		})
+	}
+}
+
+func BenchmarkContainerSerialisation(b *testing.B) {
+	var duration strings.Builder
+	var allocByte strings.Builder
+	var allocCount strings.Builder
+
+	for _, builder := range []strings.Builder{duration, allocByte, allocCount} {
+		builder.WriteString("car\tcarBase64\tcarGzip\tcarGzipBase64\tcbor\tcborBase64\tcborGzip\tcborGzipBase64\tcborFlate\tcborFlateBase64\n")
+	}
+
+	for _, tc := range []struct {
+		name   string
+		writer func(ctn Writer, w io.Writer) error
+		reader func(io.Reader) (Reader, error)
+	}{
+		{"Bytes", Writer.ToBytesWriter, FromReader},
+		{"BytesGzipped", Writer.ToBytesGzippedWriter, FromReader},
+		{"Base64StdPadding", Writer.ToBase64StdPaddingWriter, FromReader},
+		{"Base64StdPaddingGzipped", Writer.ToBase64StdPaddingGzippedWriter, FromReader},
+		{"Base64URL", Writer.ToBase64URLWriter, FromReader},
+		{"Base64URLGzip", Writer.ToBase64URLGzipWriter, FromReader},
+	} {
+		writer := NewWriter()
+
+		for i := 0; i < 10; i++ {
+			_, _, data := randToken()
+			writer.AddSealed(data)
+		}
+
+		buf := bytes.NewBuffer(nil)
+		_ = tc.writer(writer, buf)
+
+		b.Run(tc.name+"_write", func(b *testing.B) {
+			b.ReportAllocs()
+			for i := 0; i < b.N; i++ {
+				buf := bytes.NewBuffer(nil)
+				_ = tc.writer(writer, buf)
+			}
+		})
+
+		b.Run(tc.name+"_read", func(b *testing.B) {
+			b.ReportAllocs()
+			for i := 0; i < b.N; i++ {
+				_, _ = tc.reader(bytes.NewReader(buf.Bytes()))
+			}
+		})
+	}
+}
+
+func randDID() (ed25519.PrivateKey, did.DID) {
+	_, privKey, err := ed25519.GenerateKeyPair()
+	if err != nil {
+		panic(err)
+	}
+	d := didkeyctl.FromPrivateKey(privKey)
+	return privKey, d
+}
+
+func randomString(length int) string {
+	b := make([]byte, length/2+1)
+	_, _ = rand.Read(b)
+	return fmt.Sprintf("%x", b)[0:length]
+}
+
+func randToken() (*delegation.Token, cid.Cid, []byte) {
+	priv, iss := randDID()
+	_, aud := randDID()
+	cmd := command.New("foo", "bar")
+	pol := policy.MustConstruct(
+		policy.All(".[]",
+			policy.GreaterThan(".value", literal.Int(2)),
+		),
+	)
+
+	opts := []delegation.Option{
+		delegation.WithExpiration(time.Now().Add(time.Hour)),
+	}
+	for i := 0; i < 3; i++ {
+		opts = append(opts, delegation.WithMeta(randomString(8), randomString(10)))
+	}
+
+	t, err := delegation.Root(iss, aud, cmd, pol, opts...)
+	if err != nil {
+		panic(err)
+	}
+	b, c, err := t.ToSealed(priv)
+	if err != nil {
+		panic(err)
+	}
+	return t, c, b
+}
+
+func FuzzContainerRead(f *testing.F) {
+	// Generate a corpus
+	for tokenCount := 0; tokenCount < 10; tokenCount++ {
+		writer := NewWriter()
+		for i := 0; i < tokenCount; i++ {
+			_, _, data := randToken()
+			writer.AddSealed(data)
+		}
+		data, err := writer.ToBytes()
+		require.NoError(f, err)
+
+		f.Add(data)
+	}
+
+	f.Fuzz(func(t *testing.T, data []byte) {
+		start := time.Now()
+
+		// search for panics
+		_, _ = FromBytes(data)
+
+		if time.Since(start) > 100*time.Millisecond {
+			panic("too long")
+		}
+	})
+}

pkg/container/writer.go

@@ -0,0 +1,145 @@
+package container
+
+import (
+	"bytes"
+	"io"
+	"slices"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/codec/cbor"
+	"github.com/ipld/go-ipld-prime/datamodel"
+	"github.com/ipld/go-ipld-prime/fluent/qp"
+	"github.com/ipld/go-ipld-prime/node/basicnode"
+)
+
+// Writer is a token container writer. It provides a convenient way to aggregate and serialize tokens together.
+type Writer map[string]struct{}
+
+func NewWriter() Writer {
+	return make(Writer)
+}
+
+// AddSealed includes a "sealed" token (serialized with a ToSealed* function) in the container.
+func (ctn Writer) AddSealed(data []byte) {
+	ctn[string(data)] = struct{}{}
+}
+
+// ToBytes encode the container into raw bytes.
+func (ctn Writer) ToBytes() ([]byte, error) {
+	return ctn.toBytes(headerRawBytes)
+}
+
+// ToBytesWriter is the same as ToBytes, but with an io.Writer.
+func (ctn Writer) ToBytesWriter(w io.Writer) error {
+	return ctn.toWriter(headerRawBytes, w)
+}
+
+// ToBytesGzipped encode the container into gzipped bytes.
+func (ctn Writer) ToBytesGzipped() ([]byte, error) {
+	return ctn.toBytes(headerRawBytesGzip)
+}
+
+// ToBytesGzippedWriter is the same as ToBytesGzipped, but with an io.Writer.
+func (ctn Writer) ToBytesGzippedWriter(w io.Writer) error {
+	return ctn.toWriter(headerRawBytesGzip, w)
+}
+
+// ToBase64StdPadding encode the container into a base64 string, with standard encoding and padding.
+func (ctn Writer) ToBase64StdPadding() (string, error) {
+	return ctn.toString(headerBase64StdPadding)
+}
+
+// ToBase64StdPaddingWriter is the same as ToBase64StdPadding, but with an io.Writer.
+func (ctn Writer) ToBase64StdPaddingWriter(w io.Writer) error {
+	return ctn.toWriter(headerBase64StdPadding, w)
+}
+
+// ToBase64StdPaddingGzipped encode the container into a pre-gzipped base64 string, with standard encoding and padding.
+func (ctn Writer) ToBase64StdPaddingGzipped() (string, error) {
+	return ctn.toString(headerBase64StdPaddingGzip)
+}
+
+// ToBase64StdPaddingGzippedWriter is the same as ToBase64StdPaddingGzipped, but with an io.Writer.
+func (ctn Writer) ToBase64StdPaddingGzippedWriter(w io.Writer) error {
+	return ctn.toWriter(headerBase64StdPaddingGzip, w)
+}
+
+// ToBase64URL encode the container into base64 string, with URL-safe encoding and no padding.
+func (ctn Writer) ToBase64URL() (string, error) {
+	return ctn.toString(headerBase64URL)
+}
+
+// ToBase64URLWriter is the same as ToBase64URL, but with an io.Writer.
+func (ctn Writer) ToBase64URLWriter(w io.Writer) error {
+	return ctn.toWriter(headerBase64URL, w)
+}
+
+// ToBase64URLGzipped encode the container into pre-gzipped base64 string, with URL-safe encoding and no padding.
+func (ctn Writer) ToBase64URLGzipped() (string, error) {
+	return ctn.toString(headerBase64URLGzip)
+}
+
+// ToBase64URLGzipWriter is the same as ToBase64URL, but with an io.Writer.
+func (ctn Writer) ToBase64URLGzipWriter(w io.Writer) error {
+	return ctn.toWriter(headerBase64URLGzip, w)
+}
+
+func (ctn Writer) toBytes(header header) ([]byte, error) {
+	var buf bytes.Buffer
+	err := ctn.toWriter(header, &buf)
+	if err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+func (ctn Writer) toString(header header) (string, error) {
+	var buf bytes.Buffer
+	err := ctn.toWriter(header, &buf)
+	if err != nil {
+		return "", err
+	}
+	return buf.String(), nil
+}
+
+func (ctn Writer) toWriter(header header, w io.Writer) (err error) {
+	encoder := header.encoder(w)
+
+	defer func() {
+		err = encoder.Close()
+	}()
+	node, err := qp.BuildMap(basicnode.Prototype.Any, 1, func(ma datamodel.MapAssembler) {
+		qp.MapEntry(ma, containerVersionTag, qp.List(int64(len(ctn)), func(la datamodel.ListAssembler) {
+			tokens := make([][]byte, 0, len(ctn))
+			for data := range ctn {
+				tokens = append(tokens, []byte(data))
+			}
+			slices.SortFunc(tokens, bytes.Compare)
+			for _, data := range tokens {
+				qp.ListEntry(la, qp.Bytes(data))
+			}
+		}))
+	})
+	if err != nil {
+		return err
+	}
+
+	return ipld.EncodeStreaming(encoder, node, cbor.Encode)
+}
+
+// ToReader convert a container Writer into a Reader.
+// Most likely, you only want to use this in tests for convenience.
+// This is not optimized and can panic.
+func (ctn Writer) ToReader() Reader {
+	data, err := ctn.ToBytes()
+	if err != nil {
+		panic(err)
+	}
+
+	reader, err := FromBytes(data)
+	if err != nil {
+		panic(err)
+	}
+
+	return reader
+}

pkg/container/writer_test.go

@@ -0,0 +1,18 @@
+package container
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestWriterDedup(t *testing.T) {
+	ctn := NewWriter()
+
+	_, _, sealed := randToken()
+	ctn.AddSealed(sealed)
+	require.Len(t, ctn, 1)
+
+	ctn.AddSealed(sealed)
+	require.Len(t, ctn, 1)
+}

pkg/meta/meta.go

@@ -0,0 +1,265 @@
+package meta
+
+import (
+	"errors"
+	"fmt"
+	"iter"
+	"sort"
+	"strings"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/printer"
+
+	"github.com/ucan-wg/go-ucan/pkg/policy/literal"
+	"github.com/ucan-wg/go-ucan/pkg/secretbox"
+)
+
+var ErrNotFound = errors.New("key not found in meta")
+
+var ErrNotEncryptable = errors.New("value of this type cannot be encrypted")
+
+// Meta is a container for meta key-value pairs in a UCAN token.
+// This also serves as a way to construct the underlying IPLD data with minimum allocations
+// and transformations, while hiding the IPLD complexity from the caller.
+type Meta struct {
+	// This type must be compatible with the IPLD type represented by the IPLD
+	// schema { String : Any }.
+
+	Keys   []string
+	Values map[string]ipld.Node
+}
+
+// NewMeta constructs a new Meta.
+func NewMeta() *Meta {
+	return &Meta{Values: map[string]ipld.Node{}}
+}
+
+// GetBool retrieves a value as a bool.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m *Meta) GetBool(key string) (bool, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return false, ErrNotFound
+	}
+	return v.AsBool()
+}
+
+// GetString retrieves a value as a string.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m *Meta) GetString(key string) (string, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return "", ErrNotFound
+	}
+	return v.AsString()
+}
+
+// GetEncryptedString decorates GetString and decrypt its output with the given symmetric encryption key.
+func (m *Meta) GetEncryptedString(key string, encryptionKey []byte) (string, error) {
+	v, err := m.GetBytes(key)
+	if err != nil {
+		return "", err
+	}
+
+	decrypted, err := secretbox.DecryptStringWithKey(v, encryptionKey)
+	if err != nil {
+		return "", err
+	}
+
+	return string(decrypted), nil
+}
+
+// GetInt64 retrieves a value as an int64.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m *Meta) GetInt64(key string) (int64, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return 0, ErrNotFound
+	}
+	return v.AsInt()
+}
+
+// GetFloat64 retrieves a value as a float64.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m *Meta) GetFloat64(key string) (float64, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return 0, ErrNotFound
+	}
+	return v.AsFloat()
+}
+
+// GetBytes retrieves a value as a []byte.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m *Meta) GetBytes(key string) ([]byte, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return nil, ErrNotFound
+	}
+	return v.AsBytes()
+}
+
+// GetEncryptedBytes decorates GetBytes and decrypt its output with the given symmetric encryption key.
+func (m *Meta) GetEncryptedBytes(key string, encryptionKey []byte) ([]byte, error) {
+	v, err := m.GetBytes(key)
+	if err != nil {
+		return nil, err
+	}
+
+	decrypted, err := secretbox.DecryptStringWithKey(v, encryptionKey)
+	if err != nil {
+		return nil, err
+	}
+
+	return decrypted, nil
+}
+
+// GetNode retrieves a value as a raw IPLD node.
+// Returns ErrNotFound if the given key is missing.
+func (m *Meta) GetNode(key string) (ipld.Node, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return nil, ErrNotFound
+	}
+	return v, nil
+}
+
+// Add adds a key/value pair in the meta set.
+// Accepted types for val are any CBOR compatible type, or directly IPLD values.
+func (m *Meta) Add(key string, val any) error {
+	if _, ok := m.Values[key]; ok {
+		return fmt.Errorf("duplicate key %q", key)
+	}
+
+	node, err := literal.Any(val)
+	if err != nil {
+		return err
+	}
+
+	m.Keys = append(m.Keys, key)
+	m.Values[key] = node
+
+	return nil
+}
+
+// AddEncrypted adds a key/value pair in the meta set.
+// The value is encrypted with the given encryptionKey.
+// Accepted types for the value are: string, []byte.
+// The ciphertext will be 40 bytes larger than the plaintext due to encryption overhead.
+func (m *Meta) AddEncrypted(key string, val any, encryptionKey []byte) error {
+	var encrypted []byte
+	var err error
+
+	switch val := val.(type) {
+	case string:
+		encrypted, err = secretbox.EncryptWithKey([]byte(val), encryptionKey)
+		if err != nil {
+			return err
+		}
+	case []byte:
+		encrypted, err = secretbox.EncryptWithKey(val, encryptionKey)
+		if err != nil {
+			return err
+		}
+	default:
+		return ErrNotEncryptable
+	}
+
+	return m.Add(key, encrypted)
+}
+
+type Iterator interface {
+	Iter() iter.Seq2[string, ipld.Node]
+}
+
+// Include merges the provided meta into the existing one.
+//
+// If duplicate keys are encountered, the new value is silently dropped
+// without causing an error.
+func (m *Meta) Include(other Iterator) {
+	for key, value := range other.Iter() {
+		if _, ok := m.Values[key]; ok {
+			// don't overwrite
+			continue
+		}
+		m.Values[key] = value
+		m.Keys = append(m.Keys, key)
+	}
+}
+
+// Len returns the number of key/values.
+func (m *Meta) Len() int {
+	return len(m.Values)
+}
+
+// Iter iterates over the meta key/values
+func (m *Meta) Iter() iter.Seq2[string, ipld.Node] {
+	return func(yield func(string, ipld.Node) bool) {
+		for _, key := range m.Keys {
+			if !yield(key, m.Values[key]) {
+				return
+			}
+		}
+	}
+}
+
+// Equals tells if two Meta hold the same key/values.
+func (m *Meta) Equals(other *Meta) bool {
+	if len(m.Keys) != len(other.Keys) {
+		return false
+	}
+	if len(m.Values) != len(other.Values) {
+		return false
+	}
+	for _, key := range m.Keys {
+		if !ipld.DeepEqual(m.Values[key], other.Values[key]) {
+			return false
+		}
+	}
+	return true
+}
+
+func (m *Meta) String() string {
+	sort.Strings(m.Keys)
+
+	buf := strings.Builder{}
+	buf.WriteString("{")
+
+	for key, node := range m.Values {
+		buf.WriteString("\n\t")
+		buf.WriteString(key)
+		buf.WriteString(": ")
+		buf.WriteString(strings.ReplaceAll(printer.Sprint(node), "\n", "\n\t"))
+		buf.WriteString(",")
+	}
+
+	if len(m.Values) > 0 {
+		buf.WriteString("\n")
+	}
+	buf.WriteString("}")
+
+	return buf.String()
+}
+
+// ReadOnly returns a read-only version of Meta.
+func (m *Meta) ReadOnly() ReadOnly {
+	return ReadOnly{meta: m}
+}
+
+// Clone makes a deep copy.
+func (m *Meta) Clone() *Meta {
+	res := &Meta{
+		Keys:   make([]string, len(m.Keys)),
+		Values: make(map[string]ipld.Node, len(m.Values)),
+	}
+	copy(res.Keys, m.Keys)
+	for k, v := range m.Values {
+		res.Values[k] = v
+	}
+	return res
+}

pkg/meta/meta_test.go

@@ -0,0 +1,130 @@
+package meta_test
+
+import (
+	"crypto/rand"
+	"maps"
+	"testing"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/node/basicnode"
+	"github.com/stretchr/testify/require"
+
+	"github.com/ucan-wg/go-ucan/pkg/meta"
+)
+
+func TestMeta_Add(t *testing.T) {
+	t.Parallel()
+
+	type Unsupported struct{}
+
+	t.Run("error if not primitive or Node", func(t *testing.T) {
+		t.Parallel()
+
+		err := (&meta.Meta{}).Add("invalid", &Unsupported{})
+		require.Error(t, err)
+	})
+
+	t.Run("encrypted meta", func(t *testing.T) {
+		t.Parallel()
+
+		key := make([]byte, 32)
+		_, err := rand.Read(key)
+		require.NoError(t, err)
+
+		m := meta.NewMeta()
+
+		// string encryption
+		err = m.AddEncrypted("secret", "hello world", key)
+		require.NoError(t, err)
+
+		_, err = m.GetString("secret")
+		require.Error(t, err) // the ciphertext is saved as []byte instead of string
+
+		decrypted, err := m.GetEncryptedString("secret", key)
+		require.NoError(t, err)
+		require.Equal(t, "hello world", decrypted)
+
+		// bytes encryption
+		originalBytes := make([]byte, 128)
+		_, err = rand.Read(originalBytes)
+		require.NoError(t, err)
+		err = m.AddEncrypted("secret-bytes", originalBytes, key)
+		require.NoError(t, err)
+
+		encryptedBytes, err := m.GetBytes("secret-bytes")
+		require.NoError(t, err)
+		require.NotEqual(t, originalBytes, encryptedBytes)
+
+		decryptedBytes, err := m.GetEncryptedBytes("secret-bytes", key)
+		require.NoError(t, err)
+		require.Equal(t, originalBytes, decryptedBytes)
+
+		// error cases
+		t.Run("error on unsupported type", func(t *testing.T) {
+			err := m.AddEncrypted("invalid", 123, key)
+			require.ErrorIs(t, err, meta.ErrNotEncryptable)
+		})
+
+		t.Run("error on invalid key size", func(t *testing.T) {
+			err := m.AddEncrypted("invalid", "test", []byte("short-key"))
+			require.Error(t, err)
+			require.Contains(t, err.Error(), "invalid key size")
+		})
+
+		t.Run("error on nil key", func(t *testing.T) {
+			err := m.AddEncrypted("invalid", "test", nil)
+			require.Error(t, err)
+			require.Contains(t, err.Error(), "encryption key is required")
+		})
+	})
+}
+
+func TestIterCloneEquals(t *testing.T) {
+	m := meta.NewMeta()
+
+	require.NoError(t, m.Add("foo", "bar"))
+	require.NoError(t, m.Add("baz", 1234))
+
+	expected := map[string]ipld.Node{
+		"foo": basicnode.NewString("bar"),
+		"baz": basicnode.NewInt(1234),
+	}
+
+	// meta -> iter
+	require.Equal(t, expected, maps.Collect(m.Iter()))
+
+	// readonly -> iter
+	ro := m.ReadOnly()
+	require.Equal(t, expected, maps.Collect(ro.Iter()))
+
+	// meta -> clone -> iter
+	clone := m.Clone()
+	require.Equal(t, expected, maps.Collect(clone.Iter()))
+
+	// readonly -> WriteableClone -> iter
+	wclone := ro.WriteableClone()
+	require.Equal(t, expected, maps.Collect(wclone.Iter()))
+
+	require.True(t, m.Equals(wclone))
+	require.True(t, ro.Equals(wclone.ReadOnly()))
+}
+
+func TestInclude(t *testing.T) {
+	m1 := meta.NewMeta()
+
+	require.NoError(t, m1.Add("samekey", "bar"))
+	require.NoError(t, m1.Add("baz", 1234))
+
+	m2 := meta.NewMeta()
+
+	require.NoError(t, m2.Add("samekey", "othervalue")) // check no overwrite
+	require.NoError(t, m2.Add("otherkey", 1234))
+
+	m1.Include(m2)
+
+	require.Equal(t, map[string]ipld.Node{
+		"samekey":  basicnode.NewString("bar"),
+		"baz":      basicnode.NewInt(1234),
+		"otherkey": basicnode.NewInt(1234),
+	}, maps.Collect(m1.Iter()))
+}

pkg/meta/readonly.go

@@ -0,0 +1,64 @@
+package meta
+
+import (
+	"iter"
+
+	"github.com/ipld/go-ipld-prime"
+)
+
+// ReadOnly wraps a Meta into a read-only facade.
+type ReadOnly struct {
+	meta *Meta
+}
+
+func (r ReadOnly) GetBool(key string) (bool, error) {
+	return r.meta.GetBool(key)
+}
+
+func (r ReadOnly) GetString(key string) (string, error) {
+	return r.meta.GetString(key)
+}
+
+func (r ReadOnly) GetEncryptedString(key string, encryptionKey []byte) (string, error) {
+	return r.meta.GetEncryptedString(key, encryptionKey)
+}
+
+func (r ReadOnly) GetInt64(key string) (int64, error) {
+	return r.meta.GetInt64(key)
+}
+
+func (r ReadOnly) GetFloat64(key string) (float64, error) {
+	return r.meta.GetFloat64(key)
+}
+
+func (r ReadOnly) GetBytes(key string) ([]byte, error) {
+	return r.meta.GetBytes(key)
+}
+
+func (r ReadOnly) GetEncryptedBytes(key string, encryptionKey []byte) ([]byte, error) {
+	return r.meta.GetEncryptedBytes(key, encryptionKey)
+}
+
+func (r ReadOnly) GetNode(key string) (ipld.Node, error) {
+	return r.meta.GetNode(key)
+}
+
+func (r ReadOnly) Len() int {
+	return r.meta.Len()
+}
+
+func (r ReadOnly) Iter() iter.Seq2[string, ipld.Node] {
+	return r.meta.Iter()
+}
+
+func (r ReadOnly) Equals(other ReadOnly) bool {
+	return r.meta.Equals(other.meta)
+}
+
+func (r ReadOnly) String() string {
+	return r.meta.String()
+}
+
+func (r ReadOnly) WriteableClone() *Meta {
+	return r.meta.Clone()
+}

pkg/policy/glob.go

@@ -0,0 +1,79 @@
+package policy
+
+import "fmt"
+
+type glob string
+
+// parseGlob ensures that the pattern conforms to the spec: only '*' and escaped '\*' are allowed.
+func parseGlob(pattern string) (glob, error) {
+	for i := 0; i < len(pattern); i++ {
+		if pattern[i] == '*' {
+			continue
+		}
+		if pattern[i] == '\\' && i+1 < len(pattern) && pattern[i+1] == '*' {
+			i++ // skip the escaped '*'
+			continue
+		}
+		if pattern[i] == '\\' && i+1 < len(pattern) {
+			i++ // skip the escaped character
+			continue
+		}
+		if pattern[i] == '\\' {
+			return "", fmt.Errorf("invalid escape sequence")
+		}
+	}
+
+	return glob(pattern), nil
+}
+
+func mustParseGlob(pattern string) glob {
+	g, err := parseGlob(pattern)
+	if err != nil {
+		panic(err)
+	}
+	return g
+}
+
+// Match matches a string against the glob pattern with * wildcards, handling escaped '\*' literals.
+func (pattern glob) Match(str string) bool {
+	// i is the index for the pattern
+	// j is the index for the string
+	var i, j int
+
+	// starIdx keeps track of the position of the last * in the pattern.
+	// matchIdx keeps track of the position in the string where the last * matched.
+	var starIdx, matchIdx int = -1, -1
+
+	for j < len(str) {
+		if i < len(pattern) && (pattern[i] == str[j] || pattern[i] == '\\' && i+1 < len(pattern) && pattern[i+1] == str[j]) {
+			// characters match or if there's an escaped character that matches
+			if pattern[i] == '\\' {
+				// skip the escape character
+				i++
+			}
+			i++
+			j++
+		} else if i < len(pattern) && pattern[i] == '*' {
+			// there's a * wildcard in the pattern
+			starIdx = i
+			matchIdx = j
+			i++
+		} else if starIdx != -1 {
+			// there's a previous * wildcard, backtrack
+			i = starIdx + 1
+			matchIdx++
+			j = matchIdx
+		} else {
+			// no match found
+			return false
+		}
+	}
+
+	// check for remaining characters in the pattern
+	for i < len(pattern) && pattern[i] == '*' {
+		i++
+	}
+
+	// the entire pattern is processed, it's a match
+	return i == len(pattern)
+}

pkg/policy/glob_test.go

@@ -0,0 +1,73 @@
+package policy
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestSimpleGlobMatch(t *testing.T) {
+	tests := []struct {
+		pattern string
+		str     string
+		matches bool
+	}{
+		// Basic matching
+		{"*", "anything", true},
+		{"a*", "abc", true},
+		{"*c", "abc", true},
+		{"a*c", "abc", true},
+		{"a*c", "abxc", true},
+		{"a*c", "ac", true},
+		{"a*c", "a", false},
+		{"a*c", "ab", false},
+
+		// Escaped characters
+		{"a\\*c", "a*c", true},
+		{"a\\*c", "abc", false},
+
+		// Mixed wildcards and literals
+		{"a*b*c", "abc", true},
+		{"a*b*c", "aXbYc", true},
+		{"a*b*c", "aXbY", false},
+		{"a*b*c", "abYc", true},
+		{"a*b*c", "aXbc", true},
+		{"a*b*c", "aXbYcZ", false},
+
+		// Edge cases
+		{"", "", true},
+		{"", "a", false},
+		{"*", "", true},
+		{"*", "a", true},
+		{"\\*", "*", true},
+		{"\\*", "a", false},
+
+		// Specified test cases
+		{"Alice\\*, Bob*, Carol.", "Alice*, Bob, Carol.", true},
+		{"Alice\\*, Bob*, Carol.", "Alice*, Bob, Dan, Erin, Carol.", true},
+		{"Alice\\*, Bob*, Carol.", "Alice*, Bob  , Carol.", true},
+		{"Alice\\*, Bob*, Carol.", "Alice*, Bob*, Carol.", true},
+		{"Alice\\*, Bob*, Carol.", "Alice*, Bob, Carol", false},
+		{"Alice\\*, Bob*, Carol.", "Alice*, Bob*, Carol!", false},
+		{"Alice\\*, Bob*, Carol.", "Alice, Bob, Carol.", false},
+		{"Alice\\*, Bob*, Carol.", "Alice Cooper, Bob, Carol.", false},
+		{"Alice\\*, Bob*, Carol.", " Alice*, Bob, Carol. ", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.pattern+"_"+tt.str, func(t *testing.T) {
+			g, err := parseGlob(tt.pattern)
+			require.NoError(t, err)
+			require.Equal(t, tt.matches, g.Match(tt.str))
+		})
+	}
+}
+
+func BenchmarkGlob(b *testing.B) {
+	b.ReportAllocs()
+
+	for i := 0; i < b.N; i++ {
+		g := mustParseGlob("Alice\\*, Bob*, Carol.")
+		g.Match("Alice*, Bob*, Carol!")
+	}
+}

pkg/policy/ipld.go

@@ -9,10 +9,15 @@ import (
 	"github.com/ipld/go-ipld-prime/must"
 	"github.com/ipld/go-ipld-prime/node/basicnode"
 
-	"github.com/ucan-wg/go-ucan/v1/capability/policy/selector"
+	"github.com/ucan-wg/go-ucan/pkg/policy/limits"
+	"github.com/ucan-wg/go-ucan/pkg/policy/selector"
 )
 
 func FromIPLD(node datamodel.Node) (Policy, error) {
+	if err := limits.ValidateIntegerBoundsIPLD(node); err != nil {
+		return nil, fmt.Errorf("policy contains integer values outside safe bounds: %w", err)
+	}
+
 	return statementsFromIPLD("/", node)
 }
 
@@ -40,14 +45,14 @@ func statementFromIPLD(path string, node datamodel.Node) (Statement, error) {
 	}
 	op := must.String(opNode)
 
-	arg2AsSelector := func() (selector.Selector, error) {
+	arg2AsSelector := func(op string) (selector.Selector, error) {
 		nd, _ := node.LookupByIndex(1)
 		if nd.Kind() != datamodel.Kind_String {
-			return nil, ErrNotAString(path + "1/")
+			return nil, ErrNotAString(combinePath(path, op, 1))
 		}
 		sel, err := selector.Parse(must.String(nd))
 		if err != nil {
-			return nil, ErrInvalidSelector(path+"1/", err)
+			return nil, ErrInvalidSelector(combinePath(path, op, 1), err)
 		}
 		return sel, nil
 	}
@@ -57,15 +62,15 @@ func statementFromIPLD(path string, node datamodel.Node) (Statement, error) {
 		switch op {
 		case KindNot:
 			arg2, _ := node.LookupByIndex(1)
-			statement, err := statementFromIPLD(path+"1/", arg2)
+			statement, err := statementFromIPLD(combinePath(path, op, 1), arg2)
 			if err != nil {
 				return nil, err
 			}
-			return Not(statement), nil
+			return negation{statement: statement}, nil
 
 		case KindAnd, KindOr:
 			arg2, _ := node.LookupByIndex(1)
-			statement, err := statementsFromIPLD(path+"1/", arg2)
+			statement, err := statementsFromIPLD(combinePath(path, op, 1), arg2)
 			if err != nil {
 				return nil, err
 			}
@@ -76,8 +81,8 @@ func statementFromIPLD(path string, node datamodel.Node) (Statement, error) {
 		}
 	case 3:
 		switch op {
-		case KindEqual, KindLessThan, KindLessThanOrEqual, KindGreaterThan, KindGreaterThanOrEqual:
+		case KindEqual, KindNotEqual, KindLessThan, KindLessThanOrEqual, KindGreaterThan, KindGreaterThanOrEqual:
-			sel, err := arg2AsSelector()
+			sel, err := arg2AsSelector(op)
 			if err != nil {
 				return nil, err
 			}
@@ -85,28 +90,31 @@ func statementFromIPLD(path string, node datamodel.Node) (Statement, error) {
 			return equality{kind: op, selector: sel, value: arg3}, nil
 
 		case KindLike:
-			sel, err := arg2AsSelector()
+			sel, err := arg2AsSelector(op)
 			if err != nil {
 				return nil, err
 			}
 			pattern, _ := node.LookupByIndex(2)
 			if pattern.Kind() != datamodel.Kind_String {
-				return nil, ErrNotAString(path + "2/")
+				return nil, ErrNotAString(combinePath(path, op, 2))
 			}
-			res, err := Like(sel, must.String(pattern))
+			g, err := parseGlob(must.String(pattern))
 			if err != nil {
-				return nil, ErrInvalidPattern(path+"2/", err)
+				return nil, ErrInvalidPattern(combinePath(path, op, 2), err)
 			}
-			return res, nil
+			return wildcard{selector: sel, pattern: g}, nil
 
 		case KindAll, KindAny:
-			sel, err := arg2AsSelector()
+			sel, err := arg2AsSelector(op)
 			if err != nil {
 				return nil, err
 			}
-			statementsNodes, _ := node.LookupByIndex(2)
+			statementsNode, _ := node.LookupByIndex(2)
-			statements, err := statementsFromIPLD(path+"1/", statementsNodes)
+			statement, err := statementFromIPLD(combinePath(path, op, 1), statementsNode)
-			return quantifier{kind: op, selector: sel, statements: statements}, nil
+			if err != nil {
+				return nil, err
+			}
+			return quantifier{kind: op, selector: sel, statement: statement}, nil
 
 		default:
 			return nil, ErrUnrecognizedOperator(path, op)
@@ -123,7 +131,7 @@ func statementsFromIPLD(path string, node datamodel.Node) ([]Statement, error) {
 		return nil, ErrNotATuple(path)
 	}
 	if node.Length() == 0 {
-		return nil, ErrEmptyList(path)
+		return nil, nil
 	}
 
 	res := make([]Statement, node.Length())
@@ -229,7 +237,7 @@ func statementToIPLD(statement Statement) (datamodel.Node, error) {
 		if err != nil {
 			return nil, err
 		}
-		err = listBuilder.AssembleValue().AssignString(statement.pattern)
+		err = listBuilder.AssembleValue().AssignString(string(statement.pattern))
 		if err != nil {
 			return nil, err
 		}
@@ -243,7 +251,7 @@ func statementToIPLD(statement Statement) (datamodel.Node, error) {
 		if err != nil {
 			return nil, err
 		}
-		args, err := statementsToIPLD(statement.statements)
+		args, err := statementToIPLD(statement.statement)
 		if err != nil {
 			return nil, err
 		}
@@ -260,3 +268,7 @@ func statementToIPLD(statement Statement) (datamodel.Node, error) {
 
 	return list.Build(), nil
 }
+
+func combinePath(prev string, operator string, index int) string {
+	return fmt.Sprintf("%s%d-%s/", prev, index, operator)
+}

pkg/policy/ipld_errors.go

@@ -35,10 +35,6 @@ func ErrNotATuple(path string) error {
 	return errWithPath{path: path, msg: "not a tuple"}
 }
 
-func ErrEmptyList(path string) error {
-	return errWithPath{path: path, msg: "empty list"}
-}
-
 func safeStr(str string) string {
 	if len(str) > 10 {
 		return str[:10]

pkg/policy/ipld_test.go

@@ -12,21 +12,40 @@ func TestIpldRoundTrip(t *testing.T) {
 	const illustrativeExample = `
 [
   ["==", ".status", "draft"],
-    ["all", ".reviewer", [
+  ["all", ".reviewer", ["like", ".email", "*@example.com"]],
-		["like", ".email", "*@example.com"]]
+  ["any", ".tags", 
-	],
-    ["any", ".tags", [ 
     ["or", [
       ["==", ".", "news"], 
-			["==", ".", "press"]]
+      ["==", ".", "press"]
     ]]
   ]
 ]`
 
+	// must contain all the operators
+	const allOps = `
+[
+  ["and", [
+    ["==", ".foo1", ".bar1"],
+    ["!=", ".foo2", ".bar2"]
+  ]],
+  ["or", [
+    [">", ".foo5", 5.2],
+    [">=", ".foo6", 6.2]
+  ]],
+  ["not", ["like", ".foo7", "*@example.com"]],
+  ["all", ".foo8",
+    ["<", ".foo3", 3]
+  ],
+  ["any", ".foo9",
+    ["<=", ".foo4", 4]
+  ]
+]`
+
 	for _, tc := range []struct {
 		name, dagJsonStr string
 	}{
 		{"illustrativeExample", illustrativeExample},
+		{"allOps", allOps},
 	} {
 		nodes, err := ipld.Decode([]byte(tc.dagJsonStr), dagjson.Decode)
 		require.NoError(t, err)

pkg/policy/limits/int.go

@@ -0,0 +1,49 @@
+package limits
+
+import (
+	"fmt"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/must"
+)
+
+const (
+	// MaxInt53 represents the maximum safe integer in JavaScript (2^53 - 1)
+	MaxInt53 int64 = 9007199254740991
+	// MinInt53 represents the minimum safe integer in JavaScript (-2^53 + 1)
+	MinInt53 int64 = -9007199254740991
+)
+
+func ValidateIntegerBoundsIPLD(node ipld.Node) error {
+	switch node.Kind() {
+	case ipld.Kind_Int:
+		val := must.Int(node)
+		if val > MaxInt53 || val < MinInt53 {
+			return fmt.Errorf("integer value %d exceeds safe bounds", val)
+		}
+	case ipld.Kind_List:
+		it := node.ListIterator()
+		for !it.Done() {
+			_, v, err := it.Next()
+			if err != nil {
+				return err
+			}
+			if err := ValidateIntegerBoundsIPLD(v); err != nil {
+				return err
+			}
+		}
+	case ipld.Kind_Map:
+		it := node.MapIterator()
+		for !it.Done() {
+			_, v, err := it.Next()
+			if err != nil {
+				return err
+			}
+			if err := ValidateIntegerBoundsIPLD(v); err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}

pkg/policy/limits/int_test.go

@@ -0,0 +1,82 @@
+package limits
+
+import (
+	"testing"
+
+	"github.com/ipld/go-ipld-prime/datamodel"
+	"github.com/ipld/go-ipld-prime/fluent/qp"
+	"github.com/ipld/go-ipld-prime/node/basicnode"
+	"github.com/stretchr/testify/require"
+)
+
+func TestValidateIntegerBoundsIPLD(t *testing.T) {
+	buildMap := func() datamodel.Node {
+		nb := basicnode.Prototype.Any.NewBuilder()
+		qp.Map(1, func(ma datamodel.MapAssembler) {
+			qp.MapEntry(ma, "foo", qp.Int(MaxInt53+1))
+		})(nb)
+		return nb.Build()
+	}
+
+	buildList := func() datamodel.Node {
+		nb := basicnode.Prototype.Any.NewBuilder()
+		qp.List(1, func(la datamodel.ListAssembler) {
+			qp.ListEntry(la, qp.Int(MinInt53-1))
+		})(nb)
+		return nb.Build()
+	}
+
+	tests := []struct {
+		name    string
+		input   datamodel.Node
+		wantErr bool
+	}{
+		{
+			name:    "valid int",
+			input:   basicnode.NewInt(42),
+			wantErr: false,
+		},
+		{
+			name:    "max safe int",
+			input:   basicnode.NewInt(MaxInt53),
+			wantErr: false,
+		},
+		{
+			name:    "min safe int",
+			input:   basicnode.NewInt(MinInt53),
+			wantErr: false,
+		},
+		{
+			name:    "above MaxInt53",
+			input:   basicnode.NewInt(MaxInt53 + 1),
+			wantErr: true,
+		},
+		{
+			name:    "below MinInt53",
+			input:   basicnode.NewInt(MinInt53 - 1),
+			wantErr: true,
+		},
+		{
+			name:    "nested map with invalid int",
+			input:   buildMap(),
+			wantErr: true,
+		},
+		{
+			name:    "nested list with invalid int",
+			input:   buildList(),
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := ValidateIntegerBoundsIPLD(tt.input)
+			if tt.wantErr {
+				require.Error(t, err)
+				require.Contains(t, err.Error(), "exceeds safe bounds")
+			} else {
+				require.NoError(t, err)
+			}
+		})
+	}
+}

pkg/policy/literal/literal.go

@@ -0,0 +1,205 @@
+// Package literal holds a collection of functions to create IPLD types to use in policies, selector and args.
+package literal
+
+import (
+	"fmt"
+	"reflect"
+	"sort"
+
+	"github.com/ipfs/go-cid"
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/datamodel"
+	"github.com/ipld/go-ipld-prime/fluent/qp"
+	cidlink "github.com/ipld/go-ipld-prime/linking/cid"
+	"github.com/ipld/go-ipld-prime/node/basicnode"
+
+	"github.com/ucan-wg/go-ucan/pkg/policy/limits"
+)
+
+var Bool = basicnode.NewBool
+var Int = basicnode.NewInt
+var Float = basicnode.NewFloat
+var String = basicnode.NewString
+var Bytes = basicnode.NewBytes
+var Link = basicnode.NewLink
+
+func LinkCid(cid cid.Cid) ipld.Node {
+	return Link(cidlink.Link{Cid: cid})
+}
+
+func Null() ipld.Node {
+	nb := basicnode.Prototype.Any.NewBuilder()
+	nb.AssignNull()
+	return nb.Build()
+}
+
+// Map creates an IPLD node from a map[string]any
+func Map[T any](m map[string]T) (ipld.Node, error) {
+	return qp.BuildMap(basicnode.Prototype.Any, int64(len(m)), func(ma datamodel.MapAssembler) {
+		// deterministic iteration
+		keys := make([]string, 0, len(m))
+		for key := range m {
+			keys = append(keys, key)
+		}
+		sort.Strings(keys)
+		for _, key := range keys {
+			qp.MapEntry(ma, key, anyAssemble(m[key]))
+		}
+	})
+}
+
+// List creates an IPLD node from a []any
+func List[T any](l []T) (ipld.Node, error) {
+	return qp.BuildList(basicnode.Prototype.Any, int64(len(l)), func(la datamodel.ListAssembler) {
+		for _, val := range l {
+			qp.ListEntry(la, anyAssemble(val))
+		}
+	})
+}
+
+// Any creates an IPLD node from any value
+// If possible, use another dedicated function for your type for performance.
+func Any(v any) (res ipld.Node, err error) {
+	// some fast path
+	switch val := v.(type) {
+	case bool:
+		return basicnode.NewBool(val), nil
+	case string:
+		return basicnode.NewString(val), nil
+	case int:
+		i := int64(val)
+		if i > limits.MaxInt53 || i < limits.MinInt53 {
+			return nil, fmt.Errorf("integer value %d exceeds safe integer bounds", i)
+		}
+		return basicnode.NewInt(i), nil
+	case int8:
+		return basicnode.NewInt(int64(val)), nil
+	case int16:
+		return basicnode.NewInt(int64(val)), nil
+	case int32:
+		return basicnode.NewInt(int64(val)), nil
+	case int64:
+		if val > limits.MaxInt53 || val < limits.MinInt53 {
+			return nil, fmt.Errorf("integer value %d exceeds safe integer bounds", val)
+		}
+		return basicnode.NewInt(val), nil
+	case uint:
+		return basicnode.NewInt(int64(val)), nil
+	case uint8:
+		return basicnode.NewInt(int64(val)), nil
+	case uint16:
+		return basicnode.NewInt(int64(val)), nil
+	case uint32:
+		return basicnode.NewInt(int64(val)), nil
+	case uint64:
+		if val > uint64(limits.MaxInt53) {
+			return nil, fmt.Errorf("unsigned integer value %d exceeds safe integer bounds", val)
+		}
+		return basicnode.NewInt(int64(val)), nil
+	case float32:
+		return basicnode.NewFloat(float64(val)), nil
+	case float64:
+		return basicnode.NewFloat(val), nil
+	case []byte:
+		return basicnode.NewBytes(val), nil
+	case datamodel.Node:
+		return val, nil
+	case cid.Cid:
+		return LinkCid(val), nil
+	default:
+	}
+
+	builder := basicnode.Prototype__Any{}.NewBuilder()
+
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("%v", r)
+			res = nil
+		}
+	}()
+
+	anyAssemble(v)(builder)
+
+	return builder.Build(), nil
+}
+
+func anyAssemble(val any) qp.Assemble {
+	var rt reflect.Type
+	var rv reflect.Value
+
+	// support for recursive calls, staying in reflection land
+	if cast, ok := val.(reflect.Value); ok {
+		rt = cast.Type()
+		rv = cast
+	} else {
+		rt = reflect.TypeOf(val)
+		rv = reflect.ValueOf(val)
+	}
+
+	// we need to dereference in some cases, to get the real value type
+	if rt.Kind() == reflect.Ptr || rt.Kind() == reflect.Interface {
+		rv = rv.Elem()
+		rt = rv.Type()
+	}
+
+	switch rt.Kind() {
+	case reflect.Array:
+		if rt.Elem().Kind() == reflect.Uint8 {
+			panic("bytes array are not supported yet")
+		}
+		return qp.List(int64(rv.Len()), func(la datamodel.ListAssembler) {
+			for i := range rv.Len() {
+				qp.ListEntry(la, anyAssemble(rv.Index(i)))
+			}
+		})
+	case reflect.Slice:
+		if rt.Elem().Kind() == reflect.Uint8 {
+			return qp.Bytes(val.([]byte))
+		}
+		return qp.List(int64(rv.Len()), func(la datamodel.ListAssembler) {
+			for i := range rv.Len() {
+				qp.ListEntry(la, anyAssemble(rv.Index(i)))
+			}
+		})
+	case reflect.Map:
+		if rt.Key().Kind() != reflect.String {
+			break
+		}
+		// deterministic iteration
+		keys := rv.MapKeys()
+		sort.Slice(keys, func(i, j int) bool {
+			return keys[i].String() < keys[j].String()
+		})
+		return qp.Map(int64(rv.Len()), func(ma datamodel.MapAssembler) {
+			for _, key := range keys {
+				qp.MapEntry(ma, key.String(), anyAssemble(rv.MapIndex(key)))
+			}
+		})
+	case reflect.Bool:
+		return qp.Bool(rv.Bool())
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		i := rv.Int()
+		if i > limits.MaxInt53 || i < limits.MinInt53 {
+			panic(fmt.Sprintf("integer %d exceeds safe bounds", i))
+		}
+		return qp.Int(i)
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		u := rv.Uint()
+		if u > uint64(limits.MaxInt53) {
+			panic(fmt.Sprintf("unsigned integer %d exceeds safe bounds", u))
+		}
+		return qp.Int(int64(u))
+	case reflect.Float32, reflect.Float64:
+		return qp.Float(rv.Float())
+	case reflect.String:
+		return qp.String(rv.String())
+	case reflect.Struct:
+		if rt == reflect.TypeOf(cid.Cid{}) {
+			c := rv.Interface().(cid.Cid)
+			return qp.Link(cidlink.Link{Cid: c})
+		}
+	default:
+	}
+
+	panic(fmt.Sprintf("unsupported type %T", val))
+}

pkg/policy/literal/literal_test.go

@@ -0,0 +1,314 @@
+package literal
+
+import (
+	"testing"
+
+	"github.com/ipfs/go-cid"
+	"github.com/ipld/go-ipld-prime/datamodel"
+	cidlink "github.com/ipld/go-ipld-prime/linking/cid"
+	"github.com/ipld/go-ipld-prime/printer"
+	"github.com/stretchr/testify/require"
+
+	"github.com/ucan-wg/go-ucan/pkg/policy/limits"
+)
+
+func TestList(t *testing.T) {
+	n, err := List([]int{1, 2, 3})
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_List, n.Kind())
+	require.Equal(t, int64(3), n.Length())
+	require.Equal(t, `list{
+	0: int{1}
+	1: int{2}
+	2: int{3}
+}`, printer.Sprint(n))
+
+	n, err = List([][]int{{1, 2, 3}, {4, 5, 6}})
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_List, n.Kind())
+	require.Equal(t, int64(2), n.Length())
+	require.Equal(t, `list{
+	0: list{
+		0: int{1}
+		1: int{2}
+		2: int{3}
+	}
+	1: list{
+		0: int{4}
+		1: int{5}
+		2: int{6}
+	}
+}`, printer.Sprint(n))
+}
+
+func TestMap(t *testing.T) {
+	n, err := Map(map[string]any{
+		"bool":   true,
+		"string": "foobar",
+		"bytes":  []byte{1, 2, 3, 4},
+		"int":    1234,
+		"uint":   uint(12345),
+		"float":  1.45,
+		"slice":  []int{1, 2, 3},
+		"array":  [2]int{1, 2},
+		"map": map[string]any{
+			"foo": "bar",
+			"foofoo": map[string]string{
+				"barbar": "foo",
+			},
+		},
+		"link": cid.MustParse("bafzbeigai3eoy2ccc7ybwjfz5r3rdxqrinwi4rwytly24tdbh6yk7zslrm"),
+	})
+	require.NoError(t, err)
+
+	v, err := n.LookupByString("bool")
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_Bool, v.Kind())
+	require.Equal(t, true, must(v.AsBool()))
+
+	v, err = n.LookupByString("string")
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_String, v.Kind())
+	require.Equal(t, "foobar", must(v.AsString()))
+
+	v, err = n.LookupByString("bytes")
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_Bytes, v.Kind())
+	require.Equal(t, []byte{1, 2, 3, 4}, must(v.AsBytes()))
+
+	v, err = n.LookupByString("int")
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_Int, v.Kind())
+	require.Equal(t, int64(1234), must(v.AsInt()))
+
+	v, err = n.LookupByString("uint")
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_Int, v.Kind())
+	require.Equal(t, int64(12345), must(v.AsInt()))
+
+	v, err = n.LookupByString("float")
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_Float, v.Kind())
+	require.Equal(t, 1.45, must(v.AsFloat()))
+
+	v, err = n.LookupByString("slice")
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_List, v.Kind())
+	require.Equal(t, int64(3), v.Length())
+	require.Equal(t, `list{
+	0: int{1}
+	1: int{2}
+	2: int{3}
+}`, printer.Sprint(v))
+
+	v, err = n.LookupByString("array")
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_List, v.Kind())
+	require.Equal(t, int64(2), v.Length())
+	require.Equal(t, `list{
+	0: int{1}
+	1: int{2}
+}`, printer.Sprint(v))
+
+	v, err = n.LookupByString("map")
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_Map, v.Kind())
+	require.Equal(t, int64(2), v.Length())
+	require.Equal(t, `map{
+	string{"foo"}: string{"bar"}
+	string{"foofoo"}: map{
+		string{"barbar"}: string{"foo"}
+	}
+}`, printer.Sprint(v))
+
+	v, err = n.LookupByString("link")
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_Link, v.Kind())
+	asLink, err := v.AsLink()
+	require.NoError(t, err)
+	require.True(t, asLink.(cidlink.Link).Equals(cid.MustParse("bafzbeigai3eoy2ccc7ybwjfz5r3rdxqrinwi4rwytly24tdbh6yk7zslrm")))
+}
+
+func TestAny(t *testing.T) {
+	data := map[string]any{
+		"bool":   true,
+		"string": "foobar",
+		"bytes":  []byte{1, 2, 3, 4},
+		"int":    1234,
+		"uint":   uint(12345),
+		"float":  1.45,
+		"slice":  []int{1, 2, 3},
+		"array":  [2]int{1, 2},
+		"map": map[string]any{
+			"foo": "bar",
+			"foofoo": map[string]string{
+				"barbar": "foo",
+			},
+		},
+		"link": cid.MustParse("bafzbeigai3eoy2ccc7ybwjfz5r3rdxqrinwi4rwytly24tdbh6yk7zslrm"),
+		"func": func() {},
+	}
+
+	v, err := Any(data["bool"])
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_Bool, v.Kind())
+	require.Equal(t, true, must(v.AsBool()))
+
+	v, err = Any(data["string"])
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_String, v.Kind())
+	require.Equal(t, "foobar", must(v.AsString()))
+
+	v, err = Any(data["bytes"])
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_Bytes, v.Kind())
+	require.Equal(t, []byte{1, 2, 3, 4}, must(v.AsBytes()))
+
+	v, err = Any(data["int"])
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_Int, v.Kind())
+	require.Equal(t, int64(1234), must(v.AsInt()))
+
+	v, err = Any(data["uint"])
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_Int, v.Kind())
+	require.Equal(t, int64(12345), must(v.AsInt()))
+
+	v, err = Any(data["float"])
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_Float, v.Kind())
+	require.Equal(t, 1.45, must(v.AsFloat()))
+
+	v, err = Any(data["slice"])
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_List, v.Kind())
+	require.Equal(t, int64(3), v.Length())
+	require.Equal(t, `list{
+	0: int{1}
+	1: int{2}
+	2: int{3}
+}`, printer.Sprint(v))
+
+	v, err = Any(data["array"])
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_List, v.Kind())
+	require.Equal(t, int64(2), v.Length())
+	require.Equal(t, `list{
+	0: int{1}
+	1: int{2}
+}`, printer.Sprint(v))
+
+	v, err = Any(data["map"])
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_Map, v.Kind())
+	require.Equal(t, int64(2), v.Length())
+	require.Equal(t, `map{
+	string{"foo"}: string{"bar"}
+	string{"foofoo"}: map{
+		string{"barbar"}: string{"foo"}
+	}
+}`, printer.Sprint(v))
+
+	v, err = Any(data["link"])
+	require.NoError(t, err)
+	require.Equal(t, datamodel.Kind_Link, v.Kind())
+	asLink, err := v.AsLink()
+	require.NoError(t, err)
+	require.True(t, asLink.(cidlink.Link).Equals(cid.MustParse("bafzbeigai3eoy2ccc7ybwjfz5r3rdxqrinwi4rwytly24tdbh6yk7zslrm")))
+
+	_, err = Any(data["func"])
+	require.Error(t, err)
+}
+
+func BenchmarkAny(b *testing.B) {
+	b.Run("bool", func(b *testing.B) {
+		b.ReportAllocs()
+
+		for n := 0; n < b.N; n++ {
+			_, _ = Any(true)
+		}
+	})
+
+	b.Run("string", func(b *testing.B) {
+		b.ReportAllocs()
+		for n := 0; n < b.N; n++ {
+			_, _ = Any("foobar")
+		}
+	})
+
+	b.Run("bytes", func(b *testing.B) {
+		b.ReportAllocs()
+		for n := 0; n < b.N; n++ {
+			_, _ = Any([]byte{1, 2, 3, 4})
+		}
+	})
+
+	b.Run("map", func(b *testing.B) {
+		b.ReportAllocs()
+		for n := 0; n < b.N; n++ {
+			_, _ = Any(map[string]any{
+				"foo": "bar",
+				"foofoo": map[string]string{
+					"barbar": "foo",
+				},
+			})
+		}
+	})
+}
+
+func TestAnyAssembleIntegerOverflow(t *testing.T) {
+	tests := []struct {
+		name      string
+		input     interface{}
+		shouldErr bool
+	}{
+		{
+			name:      "valid int",
+			input:     42,
+			shouldErr: false,
+		},
+		{
+			name:      "max safe int",
+			input:     limits.MaxInt53,
+			shouldErr: false,
+		},
+		{
+			name:      "min safe int",
+			input:     limits.MinInt53,
+			shouldErr: false,
+		},
+		{
+			name:      "overflow int",
+			input:     int64(limits.MaxInt53 + 1),
+			shouldErr: true,
+		},
+		{
+			name:      "underflow int",
+			input:     int64(limits.MinInt53 - 1),
+			shouldErr: true,
+		},
+		{
+			name:      "overflow uint",
+			input:     uint64(limits.MaxInt53 + 1),
+			shouldErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			_, err := Any(tt.input)
+			if tt.shouldErr {
+				require.Error(t, err)
+			} else {
+				require.NoError(t, err)
+			}
+		})
+	}
+}
+
+func must[T any](t T, err error) T {
+	if err != nil {
+		panic(err)
+	}
+	return t
+}

pkg/policy/match.go

@@ -0,0 +1,306 @@
+package policy
+
+import (
+	"cmp"
+	"fmt"
+	"math"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/datamodel"
+	"github.com/ipld/go-ipld-prime/must"
+)
+
+// Match determines if the IPLD node satisfies the policy.
+// The first Statement failing to match is returned as well.
+func (p Policy) Match(node datamodel.Node) (bool, Statement) {
+	for _, stmt := range p {
+		res, leaf := matchStatement(stmt, node)
+		switch res {
+		case matchResultNoData, matchResultFalse:
+			return false, leaf
+		case matchResultOptionalNoData, matchResultTrue:
+			// continue
+		}
+	}
+	return true, nil
+}
+
+// PartialMatch returns false IIF one non-optional Statement has the corresponding data and doesn't match.
+// If the data is missing or the non-optional Statement is matching, true is returned.
+//
+// This allows performing the policy checking in multiple steps, and find immediately if a Statement already failed.
+// A final call to Match is necessary to make sure that the policy is fully matched, with no missing data
+// (apart from optional values).
+//
+// The first Statement failing to match is returned as well.
+func (p Policy) PartialMatch(node datamodel.Node) (bool, Statement) {
+	for _, stmt := range p {
+		res, leaf := matchStatement(stmt, node)
+		switch res {
+		case matchResultFalse:
+			return false, leaf
+		case matchResultNoData, matchResultOptionalNoData, matchResultTrue:
+			// continue
+		}
+	}
+	return true, nil
+}
+
+type matchResult int8
+
+const (
+	matchResultTrue           matchResult = iota // statement has data and resolve to true
+	matchResultFalse                             // statement has data and resolve to false
+	matchResultNoData                            // statement has no data
+	matchResultOptionalNoData                    // statement has no data and is optional
+)
+
+// matchStatement evaluate the policy against the given ipld.Node and returns:
+// - matchResultTrue: if the selector matched and the statement evaluated to true.
+// - matchResultFalse: if the selector matched and the statement evaluated to false.
+// - matchResultNoData: if the selector didn't match the expected data.
+// For matchResultTrue and matchResultNoData, the leaf-most (innermost) statement failing to be true is returned,
+// as well as the corresponding root-most encompassing statement.
+func matchStatement(cur Statement, node ipld.Node) (_ matchResult, leafMost Statement) {
+	var boolToRes = func(v bool) (matchResult, Statement) {
+		if v {
+			return matchResultTrue, nil
+		} else {
+			return matchResultFalse, cur
+		}
+	}
+
+	switch cur.Kind() {
+	case KindEqual:
+		if s, ok := cur.(equality); ok {
+			res, err := s.selector.Select(node)
+			if err != nil {
+				return matchResultNoData, cur
+			}
+			if res == nil { // optional selector didn't match
+				return matchResultOptionalNoData, nil
+			}
+			return boolToRes(datamodel.DeepEqual(s.value, res))
+		}
+	case KindNotEqual:
+		if s, ok := cur.(equality); ok {
+			res, err := s.selector.Select(node)
+			if err != nil {
+				return matchResultNoData, cur
+			}
+			if res == nil { // optional selector didn't match
+				return matchResultOptionalNoData, nil
+			}
+			return boolToRes(!datamodel.DeepEqual(s.value, res))
+		}
+	case KindGreaterThan:
+		if s, ok := cur.(equality); ok {
+			res, err := s.selector.Select(node)
+			if err != nil {
+				return matchResultNoData, cur
+			}
+			if res == nil { // optional selector didn't match
+				return matchResultOptionalNoData, nil
+			}
+			return boolToRes(isOrdered(s.value, res, gt))
+		}
+	case KindGreaterThanOrEqual:
+		if s, ok := cur.(equality); ok {
+			res, err := s.selector.Select(node)
+			if err != nil {
+				return matchResultNoData, cur
+			}
+			if res == nil { // optional selector didn't match
+				return matchResultOptionalNoData, nil
+			}
+			return boolToRes(isOrdered(s.value, res, gte))
+		}
+	case KindLessThan:
+		if s, ok := cur.(equality); ok {
+			res, err := s.selector.Select(node)
+			if err != nil {
+				return matchResultNoData, cur
+			}
+			if res == nil { // optional selector didn't match
+				return matchResultOptionalNoData, nil
+			}
+			return boolToRes(isOrdered(s.value, res, lt))
+		}
+	case KindLessThanOrEqual:
+		if s, ok := cur.(equality); ok {
+			res, err := s.selector.Select(node)
+			if err != nil {
+				return matchResultNoData, cur
+			}
+			if res == nil { // optional selector didn't match
+				return matchResultOptionalNoData, nil
+			}
+			return boolToRes(isOrdered(s.value, res, lte))
+		}
+	case KindNot:
+		if s, ok := cur.(negation); ok {
+			res, leaf := matchStatement(s.statement, node)
+			switch res {
+			case matchResultNoData, matchResultOptionalNoData:
+				return res, leaf
+			case matchResultTrue:
+				return matchResultFalse, cur
+			case matchResultFalse:
+				return matchResultTrue, nil
+			}
+		}
+	case KindAnd:
+		if s, ok := cur.(connective); ok {
+			for _, cs := range s.statements {
+				res, leaf := matchStatement(cs, node)
+				switch res {
+				case matchResultNoData, matchResultOptionalNoData:
+					return res, leaf
+				case matchResultTrue:
+					// continue
+				case matchResultFalse:
+					return matchResultFalse, leaf
+				}
+			}
+			return matchResultTrue, nil
+		}
+	case KindOr:
+		if s, ok := cur.(connective); ok {
+			if len(s.statements) == 0 {
+				return matchResultTrue, nil
+			}
+			for _, cs := range s.statements {
+				res, leaf := matchStatement(cs, node)
+				switch res {
+				case matchResultNoData, matchResultOptionalNoData:
+					return res, leaf
+				case matchResultTrue:
+					return matchResultTrue, leaf
+				case matchResultFalse:
+					// continue
+				}
+			}
+			return matchResultFalse, cur
+		}
+	case KindLike:
+		if s, ok := cur.(wildcard); ok {
+			res, err := s.selector.Select(node)
+			if err != nil {
+				return matchResultNoData, cur
+			}
+			if res == nil { // optional selector didn't match
+				return matchResultOptionalNoData, nil
+			}
+			v, err := res.AsString()
+			if err != nil {
+				return matchResultFalse, cur // not a string
+			}
+			return boolToRes(s.pattern.Match(v))
+		}
+	case KindAll:
+		if s, ok := cur.(quantifier); ok {
+			res, err := s.selector.Select(node)
+			if err != nil {
+				return matchResultNoData, cur
+			}
+			if res == nil {
+				return matchResultOptionalNoData, nil
+			}
+			it := res.ListIterator()
+			if it == nil {
+				return matchResultFalse, cur // not a list
+			}
+			for !it.Done() {
+				_, v, err := it.Next()
+				if err != nil {
+					panic("should never happen")
+				}
+				matchRes, leaf := matchStatement(s.statement, v)
+				switch matchRes {
+				case matchResultNoData, matchResultOptionalNoData:
+					return matchRes, leaf
+				case matchResultTrue:
+					// continue
+				case matchResultFalse:
+					return matchResultFalse, leaf
+				}
+			}
+			return matchResultTrue, nil
+		}
+	case KindAny:
+		if s, ok := cur.(quantifier); ok {
+			res, err := s.selector.Select(node)
+			if err != nil {
+				return matchResultNoData, cur
+			}
+			if res == nil {
+				return matchResultOptionalNoData, nil
+			}
+			it := res.ListIterator()
+			if it == nil {
+				return matchResultFalse, cur // not a list
+			}
+			for !it.Done() {
+				_, v, err := it.Next()
+				if err != nil {
+					panic("should never happen")
+				}
+				matchRes, leaf := matchStatement(s.statement, v)
+				switch matchRes {
+				case matchResultNoData, matchResultOptionalNoData:
+					return matchRes, leaf
+				case matchResultTrue:
+					return matchResultTrue, nil
+				case matchResultFalse:
+					// continue
+				}
+			}
+			return matchResultFalse, cur
+		}
+	}
+	panic(fmt.Errorf("unimplemented statement kind: %s", cur.Kind()))
+}
+
+// isOrdered compares two IPLD nodes and returns true if they satisfy the given ordering function.
+// It supports comparison of integers and floats, returning false for:
+//   - Nodes of different or unsupported kinds
+//   - Integer values outside JavaScript's safe integer bounds (±2^53-1)
+//   - Non-finite floating point values (NaN or ±Inf)
+//
+// The satisfies parameter is a function that interprets the comparison result:
+//   - For ">" it returns true when order is 1
+//   - For ">=" it returns true when order is 0 or 1
+//   - For "<" it returns true when order is -1
+//   - For "<=" it returns true when order is -1 or 0
+func isOrdered(expected ipld.Node, actual ipld.Node, satisfies func(order int) bool) bool {
+	if expected.Kind() == ipld.Kind_Int && actual.Kind() == ipld.Kind_Int {
+		a := must.Int(actual)
+		b := must.Int(expected)
+
+		return satisfies(cmp.Compare(a, b))
+	}
+
+	if expected.Kind() == ipld.Kind_Float && actual.Kind() == ipld.Kind_Float {
+		a, err := actual.AsFloat()
+		if err != nil {
+			panic(fmt.Errorf("extracting node float: %w", err))
+		}
+		b, err := expected.AsFloat()
+		if err != nil {
+			panic(fmt.Errorf("extracting selector float: %w", err))
+		}
+
+		if math.IsInf(a, 0) || math.IsNaN(a) || math.IsInf(b, 0) || math.IsNaN(b) {
+			return false
+		}
+
+		return satisfies(cmp.Compare(a, b))
+	}
+
+	return false
+}
+
+func gt(order int) bool  { return order == 1 }
+func gte(order int) bool { return order == 0 || order == 1 }
+func lt(order int) bool  { return order == -1 }
+func lte(order int) bool { return order == 0 || order == -1 }

pkg/policy/policy.go

@@ -0,0 +1,254 @@
+package policy
+
+// https://github.com/ucan-wg/delegation/blob/4094d5878b58f5d35055a3b93fccda0b8329ebae/README.md#policy
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/codec/dagjson"
+
+	selpkg "github.com/ucan-wg/go-ucan/pkg/policy/selector"
+)
+
+const (
+	KindEqual              = "=="   // implemented by equality
+	KindNotEqual           = "!="   // implemented by equality
+	KindGreaterThan        = ">"    // implemented by equality
+	KindGreaterThanOrEqual = ">="   // implemented by equality
+	KindLessThan           = "<"    // implemented by equality
+	KindLessThanOrEqual    = "<="   // implemented by equality
+	KindNot                = "not"  // implemented by negation
+	KindAnd                = "and"  // implemented by connective
+	KindOr                 = "or"   // implemented by connective
+	KindLike               = "like" // implemented by wildcard
+	KindAll                = "all"  // implemented by quantifier
+	KindAny                = "any"  // implemented by quantifier
+)
+
+type Policy []Statement
+
+type Constructor func() (Statement, error)
+
+func Construct(cstors ...Constructor) (Policy, error) {
+	stmts, err := assemble(cstors)
+	if err != nil {
+		return nil, err
+	}
+	return stmts, nil
+}
+
+func MustConstruct(cstors ...Constructor) Policy {
+	pol, err := Construct(cstors...)
+	if err != nil {
+		panic(err)
+	}
+	return pol
+}
+
+func (p Policy) String() string {
+	if len(p) == 0 {
+		return "[]"
+	}
+	childs := make([]string, len(p))
+	for i, statement := range p {
+		childs[i] = strings.ReplaceAll(statement.String(), "\n", "\n  ")
+	}
+	return fmt.Sprintf("[\n  %s\n]", strings.Join(childs, ",\n  "))
+}
+
+type Statement interface {
+	Kind() string
+	String() string
+}
+
+type equality struct {
+	kind     string
+	selector selpkg.Selector
+	value    ipld.Node
+}
+
+func (e equality) Kind() string {
+	return e.kind
+}
+
+func (e equality) String() string {
+	child, err := ipld.Encode(e.value, dagjson.Encode)
+	if err != nil {
+		return "ERROR: INVALID VALUE"
+	}
+	return fmt.Sprintf(`["%s", "%s", %s]`, e.kind, e.selector, strings.ReplaceAll(string(child), "\n", "\n  "))
+}
+
+func Equal(selector string, value ipld.Node) Constructor {
+	return func() (Statement, error) {
+		sel, err := selpkg.Parse(selector)
+		return equality{kind: KindEqual, selector: sel, value: value}, err
+	}
+}
+
+func NotEqual(selector string, value ipld.Node) Constructor {
+	return func() (Statement, error) {
+		sel, err := selpkg.Parse(selector)
+		return equality{kind: KindNotEqual, selector: sel, value: value}, err
+	}
+}
+
+func GreaterThan(selector string, value ipld.Node) Constructor {
+	return func() (Statement, error) {
+		sel, err := selpkg.Parse(selector)
+		return equality{kind: KindGreaterThan, selector: sel, value: value}, err
+	}
+}
+
+func GreaterThanOrEqual(selector string, value ipld.Node) Constructor {
+	return func() (Statement, error) {
+		sel, err := selpkg.Parse(selector)
+		return equality{kind: KindGreaterThanOrEqual, selector: sel, value: value}, err
+	}
+}
+
+func LessThan(selector string, value ipld.Node) Constructor {
+	return func() (Statement, error) {
+		sel, err := selpkg.Parse(selector)
+		return equality{kind: KindLessThan, selector: sel, value: value}, err
+	}
+}
+
+func LessThanOrEqual(selector string, value ipld.Node) Constructor {
+	return func() (Statement, error) {
+		sel, err := selpkg.Parse(selector)
+		return equality{kind: KindLessThanOrEqual, selector: sel, value: value}, err
+	}
+}
+
+type negation struct {
+	statement Statement
+}
+
+func (n negation) Kind() string {
+	return KindNot
+}
+
+func (n negation) String() string {
+	child := n.statement.String()
+	return fmt.Sprintf(`["%s", %s]`, n.Kind(), strings.ReplaceAll(child, "\n", "\n  "))
+}
+
+func Not(cstor Constructor) Constructor {
+	return func() (Statement, error) {
+		stmt, err := cstor()
+		return negation{statement: stmt}, err
+	}
+}
+
+type connective struct {
+	kind       string
+	statements []Statement
+}
+
+func (c connective) Kind() string {
+	return c.kind
+}
+
+func (c connective) String() string {
+	childs := make([]string, len(c.statements))
+	for i, statement := range c.statements {
+		childs[i] = strings.ReplaceAll(statement.String(), "\n", "\n  ")
+	}
+	return fmt.Sprintf("[\"%s\", [\n  %s\n]]", c.kind, strings.Join(childs, ",\n  "))
+}
+
+func And(cstors ...Constructor) Constructor {
+	return func() (Statement, error) {
+		stmts, err := assemble(cstors)
+		if err != nil {
+			return nil, err
+		}
+		return connective{kind: KindAnd, statements: stmts}, nil
+	}
+}
+
+func Or(cstors ...Constructor) Constructor {
+	return func() (Statement, error) {
+		stmts, err := assemble(cstors)
+		if err != nil {
+			return nil, err
+		}
+		return connective{kind: KindOr, statements: stmts}, nil
+	}
+}
+
+type wildcard struct {
+	selector selpkg.Selector
+	pattern  glob
+}
+
+func (n wildcard) Kind() string {
+	return KindLike
+}
+
+func (n wildcard) String() string {
+	return fmt.Sprintf(`["%s", "%s", "%s"]`, n.Kind(), n.selector, n.pattern)
+}
+
+func Like(selector string, pattern string) Constructor {
+	return func() (Statement, error) {
+		g, err := parseGlob(pattern)
+		if err != nil {
+			return nil, err
+		}
+		sel, err := selpkg.Parse(selector)
+		return wildcard{selector: sel, pattern: g}, err
+	}
+}
+
+type quantifier struct {
+	kind      string
+	selector  selpkg.Selector
+	statement Statement
+}
+
+func (n quantifier) Kind() string {
+	return n.kind
+}
+
+func (n quantifier) String() string {
+	child := n.statement.String()
+	return fmt.Sprintf("[\"%s\", \"%s\",\n  %s\n]", n.Kind(), n.selector, strings.ReplaceAll(child, "\n", "\n  "))
+}
+
+func All(selector string, cstor Constructor) Constructor {
+	return func() (Statement, error) {
+		stmt, err := cstor()
+		if err != nil {
+			return nil, err
+		}
+		sel, err := selpkg.Parse(selector)
+		return quantifier{kind: KindAll, selector: sel, statement: stmt}, err
+	}
+}
+
+func Any(selector string, cstor Constructor) Constructor {
+	return func() (Statement, error) {
+		stmt, err := cstor()
+		if err != nil {
+			return nil, err
+		}
+		sel, err := selpkg.Parse(selector)
+		return quantifier{kind: KindAny, selector: sel, statement: stmt}, err
+	}
+}
+
+func assemble(cstors []Constructor) ([]Statement, error) {
+	stmts := make([]Statement, 0, len(cstors))
+	for _, cstor := range cstors {
+		stmt, err := cstor()
+		if err != nil {
+			return nil, err
+		}
+		stmts = append(stmts, stmt)
+	}
+	return stmts, nil
+}

pkg/policy/policy_test.go

@@ -0,0 +1,95 @@
+package policy_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/ucan-wg/go-ucan/pkg/policy"
+	"github.com/ucan-wg/go-ucan/pkg/policy/literal"
+)
+
+func ExamplePolicy() {
+	pol := policy.MustConstruct(
+		policy.Equal(".status", literal.String("draft")),
+		policy.All(".reviewer",
+			policy.Like(".email", "*@example.com"),
+		),
+		policy.Any(".tags", policy.Or(
+			policy.Equal(".", literal.String("news")),
+			policy.Equal(".", literal.String("press")),
+		)),
+	)
+
+	fmt.Println(pol)
+
+	// Output:
+	// [
+	//   ["==", ".status", "draft"],
+	//   ["all", ".reviewer",
+	//     ["like", ".email", "*@example.com"]
+	//   ],
+	//   ["any", ".tags",
+	//     ["or", [
+	//       ["==", ".", "news"],
+	//       ["==", ".", "press"]
+	//     ]]
+	//   ]
+	// ]
+}
+
+func ExamplePolicy_accumulate() {
+	var statements []policy.Constructor
+
+	statements = append(statements, policy.Equal(".status", literal.String("draft")))
+
+	statements = append(statements, policy.All(".reviewer",
+		policy.Like(".email", "*@example.com"),
+	))
+
+	statements = append(statements, policy.Any(".tags", policy.Or(
+		policy.Equal(".", literal.String("news")),
+		policy.Equal(".", literal.String("press")),
+	)))
+
+	pol := policy.MustConstruct(statements...)
+
+	fmt.Println(pol)
+
+	// Output:
+	// [
+	//   ["==", ".status", "draft"],
+	//   ["all", ".reviewer",
+	//     ["like", ".email", "*@example.com"]
+	//   ],
+	//   ["any", ".tags",
+	//     ["or", [
+	//       ["==", ".", "news"],
+	//       ["==", ".", "press"]
+	//     ]]
+	//   ]
+	// ]
+}
+
+func TestConstruct(t *testing.T) {
+	pol, err := policy.Construct(
+		policy.Equal(".status", literal.String("draft")),
+		policy.All(".reviewer",
+			policy.Like(".email", "*@example.com"),
+		),
+	)
+	require.NoError(t, err)
+	require.NotNil(t, pol)
+
+	// check if errors cascade correctly
+	pol, err = policy.Construct(
+		policy.Equal(".status", literal.String("draft")),
+		policy.All(".reviewer", policy.Or(
+			policy.Like(".email", "*@example.com"),
+			policy.Like(".", "\\"), // invalid pattern
+		)),
+	)
+	require.Error(t, err)
+	require.Nil(t, pol)
+}

pkg/policy/policytest/spec.go

@@ -0,0 +1,67 @@
+package policytest
+
+import (
+	"github.com/ipld/go-ipld-prime"
+
+	"github.com/ucan-wg/go-ucan/pkg/args"
+	"github.com/ucan-wg/go-ucan/pkg/policy"
+	"github.com/ucan-wg/go-ucan/pkg/policy/literal"
+)
+
+// EmptyPolicy provides a Policy with no statements.
+var EmptyPolicy = policy.Policy{}
+
+// SpecPolicy provides a  valid Policy containing the statements that are included
+// in the second code block of the [Validation] section of the delegation specification.
+//
+// [Validation]: https://github.com/ucan-wg/delegation/tree/v1_ipld#validation
+var SpecPolicy = policy.MustConstruct(
+	policy.Equal(".from", literal.String("alice@example.com")),
+	policy.Any(".to", policy.Like(".", "*@example.com")),
+)
+
+// TODO: Replace the URL for [Validation] above when the delegation
+//       specification has been finished/merged.
+
+// SpecValidArguments provides valid, instantiated Arguments containing
+// the key/value pairs that are included in portion of the second code block
+// of the [Validation] section of the delegation specification.
+//
+// [Validation]: https://github.com/ucan-wg/delegation/tree/v1_ipld#validation
+var SpecValidArguments = args.NewBuilder().
+	Add("from", "alice@example.com").
+	Add("to", []string{
+		"bob@example.com",
+		"carol@not.example.com",
+	}).
+	Add("title", "Coffee").
+	Add("body", "Still on for coffee").
+	MustBuild()
+
+var specValidArgumentsIPLD = mustIPLD(SpecValidArguments)
+
+// SpecInvalidArguments provides invalid, instantiated Arguments containing
+// the key/value pairs that are included in portion of the second code block
+// of the [Validation] section of the delegation specification.
+//
+// [Validation]: https://github.com/ucan-wg/delegation/tree/v1_ipld#validation
+var SpecInvalidArguments = args.NewBuilder().
+	Add("from", "alice@example.com").
+	Add("to", []string{
+		"bob@null.com",
+		"carol@elsewhere.example.com",
+	}).
+	Add("title", "Coffee").
+	Add("body", "Still on for coffee").
+	MustBuild()
+
+var specInvalidArgumentsIPLD = mustIPLD(SpecInvalidArguments)
+
+func mustIPLD(args *args.Args) ipld.Node {
+	node, err := args.ToIPLD()
+	if err != nil {
+		panic(err)
+	}
+
+	return node
+}

pkg/policy/policytest/spec_test.go

@@ -0,0 +1,32 @@
+package policytest
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// TestInvocationValidation applies the example policy to the second
+// example arguments as defined in the [Validation] section of the
+// invocation specification.
+//
+// [Validation]: https://github.com/ucan-wg/delegation/tree/v1_ipld#validation
+func TestInvocationValidationSpecExamples(t *testing.T) {
+	t.Parallel()
+
+	t.Run("with passing args", func(t *testing.T) {
+		t.Parallel()
+
+		exec, stmt := SpecPolicy.Match(specValidArgumentsIPLD)
+		assert.True(t, exec)
+		assert.Nil(t, stmt)
+	})
+
+	t.Run("fails on recipients (second statement)", func(t *testing.T) {
+		t.Parallel()
+
+		exec, stmt := SpecPolicy.Match(specInvalidArgumentsIPLD)
+		assert.False(t, exec)
+		assert.NotNil(t, stmt)
+	})
+}

pkg/policy/selector/parsing.go

@@ -0,0 +1,209 @@
+package selector
+
+import (
+	"fmt"
+	"math"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"github.com/ucan-wg/go-ucan/pkg/policy/limits"
+)
+
+var (
+	indexRegex = regexp.MustCompile(`^-?\d+$`)
+	sliceRegex = regexp.MustCompile(`^((\-?\d+:\-?\d*)|(\-?\d*:\-?\d+))$`)
+
+	// Field name requirements:
+	// - Must start with ASCII letter, Unicode letter, or underscore
+	// - Can contain:
+	//   - ASCII letters (a-z, A-Z)
+	//   - ASCII digits (0-9)
+	//   - Unicode letters (\p{L})
+	//   - Dollar sign ($)
+	//   - Underscore (_)
+	//   - Hyphen (-)
+	fieldRegex = regexp.MustCompile(`^\.[a-zA-Z_\p{L}][a-zA-Z0-9$_\p{L}\-]*$`)
+)
+
+func Parse(str string) (Selector, error) {
+	if len(str) == 0 {
+		return nil, newParseError("empty selector", str, 0, "")
+	}
+	if string(str[0]) != "." {
+		return nil, newParseError("selector must start with identity segment '.'", str, 0, string(str[0]))
+	}
+	if str == "." {
+		return Selector{segment{str: ".", identity: true}}, nil
+	}
+	if str == ".?" {
+		return Selector{segment{str: ".?", identity: true, optional: true}}, nil
+	}
+
+	col := 0
+	var sel Selector
+	for _, tok := range tokenize(str) {
+		seg := tok
+		opt := strings.HasSuffix(tok, "?")
+		if opt {
+			seg = strings.TrimRight(tok, "?")
+		}
+		switch {
+		case seg == ".":
+			if len(sel) > 0 && sel[len(sel)-1].Identity() {
+				return nil, newParseError("selector contains unsupported recursive descent segment: '..'", str, col, tok)
+			}
+			sel = append(sel, segment{str: ".", identity: true})
+
+		case seg == "[]":
+			sel = append(sel, segment{str: tok, optional: opt, iterator: true})
+
+		case strings.HasPrefix(seg, "[") && strings.HasSuffix(seg, "]"):
+			lookup := seg[1 : len(seg)-1]
+
+			switch {
+			// index, [123]
+			case indexRegex.MatchString(lookup):
+				idx, err := strconv.Atoi(lookup)
+				if err != nil {
+					return nil, newParseError("invalid index", str, col, tok)
+				}
+				if int64(idx) > limits.MaxInt53 || int64(idx) < limits.MinInt53 {
+					return nil, newParseError(fmt.Sprintf("index %d exceeds safe integer bounds", idx), str, col, tok)
+				}
+				sel = append(sel, segment{str: tok, optional: opt, index: idx})
+
+			// explicit field, ["abcd"]
+			case strings.HasPrefix(lookup, "\"") && strings.HasSuffix(lookup, "\""):
+				fieldName := lookup[1 : len(lookup)-1]
+				if strings.Contains(fieldName, ":") {
+					return nil, newParseError(fmt.Sprintf("invalid segment: %s", seg), str, col, tok)
+				}
+				sel = append(sel, segment{str: tok, optional: opt, field: fieldName})
+
+			// slice [3:5] or [:5] or [3:], also negative numbers
+			case sliceRegex.MatchString(lookup):
+				var rng [2]int64
+				splt := strings.Split(lookup, ":")
+				if splt[0] == "" {
+					rng[0] = math.MinInt
+				} else {
+					i, err := strconv.ParseInt(splt[0], 10, 0)
+					if err != nil {
+						return nil, newParseError("invalid slice index", str, col, tok)
+					}
+					if i > limits.MaxInt53 || i < limits.MinInt53 {
+						return nil, newParseError(fmt.Sprintf("slice index %d exceeds safe integer bounds", i), str, col, tok)
+					}
+					rng[0] = i
+				}
+				if splt[1] == "" {
+					rng[1] = math.MaxInt
+				} else {
+					i, err := strconv.ParseInt(splt[1], 10, 0)
+					if err != nil {
+						return nil, newParseError("invalid slice index", str, col, tok)
+					}
+					if i > limits.MaxInt53 || i < limits.MinInt53 {
+						return nil, newParseError(fmt.Sprintf("slice index %d exceeds safe integer bounds", i), str, col, tok)
+					}
+					rng[1] = i
+				}
+				sel = append(sel, segment{str: tok, optional: opt, slice: rng[:]})
+
+			default:
+				return nil, newParseError(fmt.Sprintf("invalid segment: %s", seg), str, col, tok)
+			}
+
+		case fieldRegex.MatchString(seg):
+			sel = append(sel, segment{str: tok, optional: opt, field: seg[1:]})
+		default:
+			return nil, newParseError(fmt.Sprintf("invalid segment: %s", seg), str, col, tok)
+		}
+		col += len(tok)
+	}
+	return sel, nil
+}
+
+func MustParse(sel string) Selector {
+	s, err := Parse(sel)
+	if err != nil {
+		panic(err)
+	}
+	return s
+}
+
+func tokenize(str string) []string {
+	var toks []string
+	col := 0
+	ofs := 0
+	ctx := ""
+
+	for col < len(str) {
+		char := string(str[col])
+
+		if char == "\"" && string(str[col-1]) != "\\" {
+			col++
+			if ctx == "\"" {
+				ctx = ""
+			} else {
+				ctx = "\""
+			}
+			continue
+		}
+
+		if ctx == "\"" {
+			col++
+			continue
+		}
+
+		if char == "." || char == "[" {
+			if ofs < col {
+				toks = append(toks, str[ofs:col])
+			}
+			ofs = col
+		}
+		col++
+	}
+
+	if ofs < col && ctx != "\"" {
+		toks = append(toks, str[ofs:col])
+	}
+
+	return toks
+}
+
+type parseErr struct {
+	msg string
+	src string
+	col int
+	tok string
+}
+
+func (p parseErr) Name() string {
+	return "ParseError"
+}
+
+func (p parseErr) Message() string {
+	return p.msg
+}
+
+func (p parseErr) Column() int {
+	return p.col
+}
+
+func (p parseErr) Error() string {
+	return p.msg
+}
+
+func (p parseErr) Source() string {
+	return p.src
+}
+
+func (p parseErr) Token() string {
+	return p.tok
+}
+
+func newParseError(message string, source string, column int, token string) error {
+	return parseErr{message, source, column, token}
+}

pkg/policy/selector/parsing_test.go

@@ -0,0 +1,641 @@
+package selector
+
+import (
+	"fmt"
+	"math"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/ucan-wg/go-ucan/pkg/policy/limits"
+)
+
+func TestParse(t *testing.T) {
+	t.Run("identity", func(t *testing.T) {
+		sel, err := Parse(".")
+		require.NoError(t, err)
+		require.Equal(t, 1, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+	})
+
+	t.Run("dotted field name", func(t *testing.T) {
+		sel, err := Parse(".foo")
+		require.NoError(t, err)
+		require.Equal(t, 1, len(sel))
+		require.False(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Equal(t, sel[0].Field(), "foo")
+		require.Empty(t, sel[0].Index())
+
+		sel, err = Parse(".foo_bar")
+		require.NoError(t, err)
+		require.Equal(t, 1, len(sel))
+		require.False(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Equal(t, sel[0].Field(), "foo_bar")
+		require.Empty(t, sel[0].Index())
+
+		sel, err = Parse(".foo-bar")
+		require.NoError(t, err)
+		require.Equal(t, 1, len(sel))
+		require.False(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Equal(t, sel[0].Field(), "foo-bar")
+		require.Empty(t, sel[0].Index())
+
+		sel, err = Parse(".foo*bar")
+		require.ErrorContains(t, err, "invalid segment")
+	})
+
+	t.Run("explicit field", func(t *testing.T) {
+		sel, err := Parse(`.["foo"]`)
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.False(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Empty(t, sel[1].Slice())
+		require.Equal(t, sel[1].Field(), "foo")
+		require.Empty(t, sel[1].Index())
+	})
+
+	t.Run("iterator, collection value", func(t *testing.T) {
+		sel, err := Parse(".[]")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.False(t, sel[1].Optional())
+		require.True(t, sel[1].Iterator())
+		require.Empty(t, sel[1].Slice())
+		require.Empty(t, sel[1].Field())
+		require.Empty(t, sel[1].Index())
+	})
+
+	t.Run("index", func(t *testing.T) {
+		sel, err := Parse(".[138]")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.False(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Empty(t, sel[1].Slice())
+		require.Empty(t, sel[1].Field())
+		require.Equal(t, sel[1].Index(), 138)
+	})
+
+	t.Run("negative index", func(t *testing.T) {
+		sel, err := Parse(".[-138]")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.False(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Empty(t, sel[1].Slice())
+		require.Empty(t, sel[1].Field())
+		require.Equal(t, sel[1].Index(), -138)
+	})
+
+	t.Run("List slice", func(t *testing.T) {
+		sel, err := Parse(".[7:11]")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.False(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Equal(t, sel[1].Slice(), []int64{7, 11})
+		require.Empty(t, sel[1].Field())
+		require.Empty(t, sel[1].Index())
+
+		sel, err = Parse(".[2:]")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.False(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Equal(t, sel[1].Slice(), []int64{2, math.MaxInt})
+		require.Empty(t, sel[1].Field())
+		require.Empty(t, sel[1].Index())
+
+		sel, err = Parse(".[:42]")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.False(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Equal(t, sel[1].Slice(), []int64{math.MinInt, 42})
+		require.Empty(t, sel[1].Field())
+		require.Empty(t, sel[1].Index())
+
+		sel, err = Parse(".[0:-2]")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.False(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Equal(t, sel[1].Slice(), []int64{0, -2})
+		require.Empty(t, sel[1].Field())
+		require.Empty(t, sel[1].Index())
+	})
+
+	t.Run("optional identity", func(t *testing.T) {
+		sel, err := Parse(".?")
+		require.NoError(t, err)
+		require.Equal(t, 1, len(sel))
+		require.True(t, sel[0].Identity())
+		require.True(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+	})
+
+	t.Run("optional dotted field name", func(t *testing.T) {
+		sel, err := Parse(".foo?")
+		require.NoError(t, err)
+		require.Equal(t, 1, len(sel))
+		require.False(t, sel[0].Identity())
+		require.True(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Equal(t, sel[0].Field(), "foo")
+		require.Empty(t, sel[0].Index())
+	})
+
+	t.Run("optional explicit field", func(t *testing.T) {
+		sel, err := Parse(`.["foo"]?`)
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.True(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Empty(t, sel[1].Slice())
+		require.Equal(t, sel[1].Field(), "foo")
+		require.Empty(t, sel[1].Index())
+	})
+
+	t.Run("optional iterator", func(t *testing.T) {
+		sel, err := Parse(".[]?")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.True(t, sel[1].Optional())
+		require.True(t, sel[1].Iterator())
+		require.Empty(t, sel[1].Slice())
+		require.Empty(t, sel[1].Field())
+		require.Empty(t, sel[1].Index())
+	})
+
+	t.Run("optional index", func(t *testing.T) {
+		sel, err := Parse(".[138]?")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.True(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Empty(t, sel[1].Slice())
+		require.Empty(t, sel[1].Field())
+		require.Equal(t, sel[1].Index(), 138)
+	})
+
+	t.Run("optional negative index", func(t *testing.T) {
+		sel, err := Parse(".[-138]?")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.True(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Empty(t, sel[1].Slice())
+		require.Empty(t, sel[1].Field())
+		require.Equal(t, sel[1].Index(), -138)
+	})
+
+	t.Run("optional list slice", func(t *testing.T) {
+		sel, err := Parse(".[7:11]?")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.True(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Equal(t, sel[1].Slice(), []int64{7, 11})
+		require.Empty(t, sel[1].Field())
+		require.Empty(t, sel[1].Index())
+
+		sel, err = Parse(".[2:]?")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.True(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Equal(t, sel[1].Slice(), []int64{2, math.MaxInt})
+		require.Empty(t, sel[1].Field())
+		require.Empty(t, sel[1].Index())
+
+		sel, err = Parse(".[:42]?")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.True(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Equal(t, sel[1].Slice(), []int64{math.MinInt, 42})
+		require.Empty(t, sel[1].Field())
+		require.Empty(t, sel[1].Index())
+
+		sel, err = Parse(".[0:-2]?")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.True(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Equal(t, sel[1].Slice(), []int64{0, -2})
+		require.Empty(t, sel[1].Field())
+		require.Empty(t, sel[1].Index())
+	})
+
+	t.Run("idempotent optional", func(t *testing.T) {
+		sel, err := Parse(".foo???")
+		require.NoError(t, err)
+		require.Equal(t, 1, len(sel))
+		require.False(t, sel[0].Identity())
+		require.True(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Equal(t, sel[0].Field(), "foo")
+		require.Empty(t, sel[0].Index())
+	})
+
+	t.Run("deny multi dot", func(t *testing.T) {
+		_, err := Parse("..")
+		require.Error(t, err)
+	})
+
+	t.Run("nesting", func(t *testing.T) {
+		str := `.foo.["bar"].[138]?.baz[1:]`
+		sel, err := Parse(str)
+		require.NoError(t, err)
+		require.Equal(t, str, sel.String())
+		require.Equal(t, 7, len(sel))
+		require.False(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Equal(t, sel[0].Field(), "foo")
+		require.Empty(t, sel[0].Index())
+		require.True(t, sel[1].Identity())
+		require.False(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Empty(t, sel[1].Slice())
+		require.Empty(t, sel[1].Field())
+		require.Empty(t, sel[1].Index())
+		require.False(t, sel[2].Identity())
+		require.False(t, sel[2].Optional())
+		require.False(t, sel[2].Iterator())
+		require.Empty(t, sel[2].Slice())
+		require.Equal(t, sel[2].Field(), "bar")
+		require.Empty(t, sel[2].Index())
+		require.True(t, sel[3].Identity())
+		require.False(t, sel[3].Optional())
+		require.False(t, sel[3].Iterator())
+		require.Empty(t, sel[3].Slice())
+		require.Empty(t, sel[3].Field())
+		require.Empty(t, sel[3].Index())
+		require.False(t, sel[4].Identity())
+		require.True(t, sel[4].Optional())
+		require.False(t, sel[4].Iterator())
+		require.Empty(t, sel[4].Slice())
+		require.Empty(t, sel[4].Field())
+		require.Equal(t, sel[4].Index(), 138)
+		require.False(t, sel[5].Identity())
+		require.False(t, sel[5].Optional())
+		require.False(t, sel[5].Iterator())
+		require.Empty(t, sel[5].Slice())
+		require.Equal(t, sel[5].Field(), "baz")
+		require.Empty(t, sel[5].Index())
+		require.False(t, sel[6].Identity())
+		require.False(t, sel[6].Optional())
+		require.False(t, sel[6].Iterator())
+		require.Equal(t, sel[6].Slice(), []int64{1, math.MaxInt})
+		require.Empty(t, sel[6].Field())
+		require.Empty(t, sel[6].Index())
+	})
+
+	t.Run("non dotted", func(t *testing.T) {
+		_, err := Parse("foo")
+		require.NotNil(t, err)
+	})
+
+	t.Run("non quoted", func(t *testing.T) {
+		_, err := Parse(".[foo]")
+		require.NotNil(t, err)
+	})
+
+	t.Run("slice with negative start and positive end", func(t *testing.T) {
+		sel, err := Parse(".[0:-2]")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.False(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Equal(t, sel[1].Slice(), []int64{0, -2})
+		require.Empty(t, sel[1].Field())
+		require.Empty(t, sel[1].Index())
+	})
+
+	t.Run("slice with start greater than end", func(t *testing.T) {
+		sel, err := Parse(".[5:2]")
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.False(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Equal(t, sel[1].Slice(), []int64{5, 2})
+		require.Empty(t, sel[1].Field())
+		require.Empty(t, sel[1].Index())
+	})
+
+	t.Run("slice on string", func(t *testing.T) {
+		sel, err := Parse(`.["foo"].[1:3]`)
+		require.NoError(t, err)
+		require.Equal(t, 4, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.False(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Empty(t, sel[1].Slice())
+		require.Equal(t, sel[1].Field(), "foo")
+		require.Empty(t, sel[1].Index())
+		require.True(t, sel[2].Identity())
+		require.False(t, sel[2].Optional())
+		require.False(t, sel[2].Iterator())
+		require.Empty(t, sel[2].Slice())
+		require.Empty(t, sel[2].Field())
+		require.Empty(t, sel[2].Index())
+		require.False(t, sel[3].Identity())
+		require.False(t, sel[3].Optional())
+		require.False(t, sel[3].Iterator())
+		require.Equal(t, sel[3].Slice(), []int64{1, 3})
+		require.Empty(t, sel[3].Field())
+		require.Empty(t, sel[3].Index())
+	})
+
+	t.Run("slice on array", func(t *testing.T) {
+		sel, err := Parse(`.[1:3]`)
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.False(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Equal(t, sel[1].Slice(), []int64{1, 3})
+		require.Empty(t, sel[1].Field())
+		require.Empty(t, sel[1].Index())
+	})
+
+	t.Run("index on array", func(t *testing.T) {
+		sel, err := Parse(`.[1]`)
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.False(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Empty(t, sel[1].Slice())
+		require.Empty(t, sel[1].Field())
+		require.Equal(t, sel[1].Index(), 1)
+	})
+
+	t.Run("invalid slice on object", func(t *testing.T) {
+		_, err := Parse(`.["foo":"bar"]`)
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "invalid segment")
+	})
+
+	t.Run("index on object", func(t *testing.T) {
+		sel, err := Parse(`.["foo"]`)
+		require.NoError(t, err)
+		require.Equal(t, 2, len(sel))
+		require.True(t, sel[0].Identity())
+		require.False(t, sel[0].Optional())
+		require.False(t, sel[0].Iterator())
+		require.Empty(t, sel[0].Slice())
+		require.Empty(t, sel[0].Field())
+		require.Empty(t, sel[0].Index())
+		require.False(t, sel[1].Identity())
+		require.False(t, sel[1].Optional())
+		require.False(t, sel[1].Iterator())
+		require.Empty(t, sel[1].Slice())
+		require.Equal(t, sel[1].Field(), "foo")
+		require.Empty(t, sel[1].Index())
+	})
+
+	t.Run("slice with non-integer start", func(t *testing.T) {
+		_, err := Parse(".[foo:3]")
+		require.Error(t, err)
+	})
+
+	t.Run("slice with non-integer end", func(t *testing.T) {
+		_, err := Parse(".[1:bar]")
+		require.Error(t, err)
+	})
+
+	t.Run("index with non-integer", func(t *testing.T) {
+		_, err := Parse(".[foo]")
+		require.Error(t, err)
+	})
+
+	t.Run("extended field names", func(t *testing.T) {
+		validFields := []string{
+			".basic",
+			".user_name",
+			".user-name",
+			".userName$special",
+			".αβγ",        // Greek letters
+			".użytkownik", // Polish characters
+			".用户",         // Chinese characters
+			".사용자",        // Korean characters
+			"._private",
+			".number123",
+			".camelCase",
+			".snake_case",
+			".kebab-case",
+			".mixed_kebab-case",
+			".with$dollar",
+			".MIXED_Case_123",
+			".unicodeø",
+		}
+
+		for _, field := range validFields {
+			sel, err := Parse(field)
+			require.NoError(t, err, "field: %s", field)
+			require.NotNil(t, sel)
+		}
+
+		invalidFields := []string{
+			".123number",         // Can't start with digit
+			".@special",          // @ not allowed
+			".space name",        // No spaces
+			".#hashtag",          // No #
+			".name!",             // No !
+			".{brackets}",        // No brackets
+			".name/with/slashes", // No slashes
+		}
+
+		for _, field := range invalidFields {
+			sel, err := Parse(field)
+			require.Error(t, err, "field: %s", field)
+			require.Nil(t, sel)
+		}
+	})
+
+	t.Run("integer overflow", func(t *testing.T) {
+		sel, err := Parse(fmt.Sprintf(".[%d]", limits.MaxInt53+1))
+		require.Error(t, err)
+		require.Nil(t, sel)
+
+		sel, err = Parse(fmt.Sprintf(".[%d]", limits.MinInt53-1))
+		require.Error(t, err)
+		require.Nil(t, sel)
+
+		// Test slice overflow
+		sel, err = Parse(fmt.Sprintf(".[%d:42]", limits.MaxInt53+1))
+		require.Error(t, err)
+		require.Nil(t, sel)
+
+		sel, err = Parse(fmt.Sprintf(".[1:%d]", limits.MaxInt53+1))
+		require.Error(t, err)
+		require.Nil(t, sel)
+	})
+}

pkg/policy/selector/selector.go

@@ -0,0 +1,342 @@
+package selector
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+	"strings"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/datamodel"
+	"github.com/ipld/go-ipld-prime/fluent/qp"
+	"github.com/ipld/go-ipld-prime/node/basicnode"
+)
+
+// Selector describes a UCAN policy selector, as specified here:
+// https://github.com/ucan-wg/delegation/blob/4094d5878b58f5d35055a3b93fccda0b8329ebae/README.md#selectors
+type Selector []segment
+
+// Select perform the selection described by the selector on the input IPLD DAG.
+// Select can return:
+//   - exactly one matched IPLD node
+//   - a resolutionErr error if not being able to resolve to a node
+//   - nil and no errors, if the selector couldn't match on an optional segment (with ?).
+func (s Selector) Select(subject ipld.Node) (ipld.Node, error) {
+	return resolve(s, subject, nil)
+}
+
+func (s Selector) String() string {
+	var res strings.Builder
+	for _, seg := range s {
+		res.WriteString(seg.String())
+	}
+	return res.String()
+}
+
+type segment struct {
+	str      string
+	identity bool
+	optional bool
+	iterator bool
+	slice    []int64 // either 0-length or 2-length
+	field    string
+	index    int
+}
+
+// String returns the segment's string representation.
+func (s segment) String() string {
+	return s.str
+}
+
+// Identity flags that this selector is the identity selector.
+func (s segment) Identity() bool {
+	return s.identity
+}
+
+// Optional flags that this selector is optional.
+func (s segment) Optional() bool {
+	return s.optional
+}
+
+// Iterator flags that this selector is an iterator segment.
+func (s segment) Iterator() bool {
+	return s.iterator
+}
+
+// Slice flags that this segment targets a range of a slice.
+func (s segment) Slice() []int64 {
+	return s.slice
+}
+
+// Field is the name of a field in a struct/map.
+func (s segment) Field() string {
+	return s.field
+}
+
+// Index is an index of a slice.
+func (s segment) Index() int {
+	return s.index
+}
+
+func resolve(sel Selector, subject ipld.Node, at []string) (ipld.Node, error) {
+	errIfNotOptional := func(s segment, err error) error {
+		if !s.Optional() {
+			return err
+		}
+		return nil
+	}
+
+	cur := subject
+	for _, seg := range sel {
+		// 1st level: handle the different segment types (iterator, field, slice, index)
+		// 2nd level: handle different node kinds (list, map, string, bytes)
+		switch {
+		case seg.Identity():
+			continue
+
+		case seg.Iterator():
+			switch {
+			case cur == nil || cur.Kind() == datamodel.Kind_Null:
+				if seg.Optional() {
+					// build an empty list
+					n, _ := qp.BuildList(basicnode.Prototype.Any, 0, func(_ datamodel.ListAssembler) {})
+					return n, nil
+				}
+				return nil, newResolutionError(fmt.Sprintf("can not iterate over kind: %s", kindString(cur)), at)
+
+			case cur.Kind() == datamodel.Kind_List:
+				// iterators are no-op on list
+				continue
+
+			case cur.Kind() == datamodel.Kind_Map:
+				// iterators on maps collect the values
+				nd, err := qp.BuildList(basicnode.Prototype.Any, cur.Length(), func(l datamodel.ListAssembler) {
+					it := cur.MapIterator()
+					for !it.Done() {
+						_, v, err := it.Next()
+						if err != nil {
+							// recovered by BuildList
+							// Error is bubbled up, but should never occur as we already checked the type,
+							// and are using the iterator correctly.
+							// This is verified with fuzzing.
+							panic(err)
+						}
+						qp.ListEntry(l, qp.Node(v))
+					}
+				})
+				if err != nil {
+					panic("should never happen")
+				}
+				return nd, nil
+
+			default:
+				return nil, newResolutionError(fmt.Sprintf("can not iterate over kind: %s", kindString(cur)), at)
+			}
+
+		case seg.Field() != "":
+			at = append(at, seg.Field())
+			switch {
+			case cur == nil:
+				err := newResolutionError(fmt.Sprintf("can not access field: %s on kind: %s", seg.Field(), kindString(cur)), at)
+				return nil, errIfNotOptional(seg, err)
+
+			case cur.Kind() == datamodel.Kind_Map:
+				n, err := cur.LookupByString(seg.Field())
+				if err != nil {
+					// the only possible error is missing field as we already check the type
+					if seg.Optional() {
+						cur = nil
+					} else {
+						return nil, newResolutionError(fmt.Sprintf("object has no field named: %s", seg.Field()), at)
+					}
+				} else {
+					cur = n
+				}
+
+			default:
+				err := newResolutionError(fmt.Sprintf("can not access field: %s on kind: %s", seg.Field(), kindString(cur)), at)
+				return nil, errIfNotOptional(seg, err)
+			}
+
+		case len(seg.Slice()) > 0:
+			if cur == nil {
+				err := newResolutionError(fmt.Sprintf("can not slice on kind: %s", kindString(cur)), at)
+				return nil, errIfNotOptional(seg, err)
+			}
+
+			slice := seg.Slice()
+
+			switch cur.Kind() {
+			case datamodel.Kind_List:
+				start, end := resolveSliceIndices(slice, cur.Length())
+				sliced, err := qp.BuildList(basicnode.Prototype.Any, end-start, func(l datamodel.ListAssembler) {
+					for i := start; i < end; i++ {
+						item, err := cur.LookupByIndex(i)
+						if err != nil {
+							// recovered by BuildList
+							// Error is bubbled up, but should never occur as we already checked the type and boundaries
+							// This is verified with fuzzing.
+							panic(err)
+						}
+						qp.ListEntry(l, qp.Node(item))
+					}
+				})
+				if err != nil {
+					panic("should never happen")
+				}
+				cur = sliced
+
+			case datamodel.Kind_Bytes:
+				b, _ := cur.AsBytes()
+				start, end := resolveSliceIndices(slice, int64(len(b)))
+				cur = basicnode.NewBytes(b[start:end])
+
+			case datamodel.Kind_String:
+				str, _ := cur.AsString()
+				runes := []rune(str)
+				start, end := resolveSliceIndices(slice, int64(len(runes)))
+				cur = basicnode.NewString(string(runes[start:end]))
+
+			default:
+				return nil, newResolutionError(fmt.Sprintf("can not slice on kind: %s", kindString(cur)), at)
+			}
+
+		default: // Index()
+			at = append(at, strconv.Itoa(seg.Index()))
+
+			if cur == nil {
+				err := newResolutionError(fmt.Sprintf("can not access index: %d on kind: %s", seg.Index(), kindString(cur)), at)
+				return nil, errIfNotOptional(seg, err)
+			}
+
+			idx := seg.Index()
+			switch cur.Kind() {
+			case datamodel.Kind_List:
+				if idx < 0 {
+					idx = int(cur.Length()) + idx
+				}
+				if idx < 0 || idx >= int(cur.Length()) {
+					err := newResolutionError(fmt.Sprintf("index out of bounds: %d", seg.Index()), at)
+					return nil, errIfNotOptional(seg, err)
+				}
+				cur, _ = cur.LookupByIndex(int64(idx))
+
+			case datamodel.Kind_Bytes:
+				b, _ := cur.AsBytes()
+				if idx < 0 {
+					idx = len(b) + idx
+				}
+				if idx < 0 || idx >= len(b) {
+					err := newResolutionError(fmt.Sprintf("index %d out of bounds for bytes of length %d", seg.Index(), len(b)), at)
+					return nil, errIfNotOptional(seg, err)
+				}
+				cur = basicnode.NewInt(int64(b[idx]))
+
+			default:
+				return nil, newResolutionError(fmt.Sprintf("can not access index: %d on kind: %s", seg.Index(), kindString(cur)), at)
+			}
+		}
+	}
+
+	// segment exhausted, we return where we are
+	return cur, nil
+}
+
+// resolveSliceIndices resolves the start and end indices for slicing a list or byte array.
+//
+// It takes the slice indices from the selector segment and the length of the list or byte array,
+// and returns the resolved start and end indices. Negative indices are supported.
+//
+// Parameters:
+//   - slice: The slice indices from the selector segment.
+//   - length: The length of the list or byte array being sliced.
+//
+// Returns:
+//   - start: The resolved start index for slicing.
+//   - end: The resolved **excluded** end index for slicing.
+func resolveSliceIndices(slice []int64, length int64) (start int64, end int64) {
+	if len(slice) != 2 {
+		panic("should always be 2-length")
+	}
+
+	start, end = slice[0], slice[1]
+
+	// adjust boundaries
+	switch {
+	case slice[0] == math.MinInt:
+		start = 0
+	case slice[0] < 0:
+		// Check for potential overflow before adding
+		if -slice[0] > length {
+			start = 0
+		} else {
+			start = length + slice[0]
+		}
+	}
+
+	switch {
+	case slice[1] == math.MaxInt:
+		end = length
+	case slice[1] < 0:
+		// Check for potential overflow before adding
+		if -slice[1] > length {
+			end = 0
+		} else {
+			end = length + slice[1]
+		}
+	}
+
+	// backward iteration is not allowed, shortcut to an empty result
+	if start >= end {
+		start, end = 0, 0
+		return
+	}
+
+	// clamp out of bound
+	if start < 0 {
+		start = 0
+	}
+	if start > length {
+		start = length
+	}
+	if end < 0 {
+		end = 0
+	}
+	if end > length {
+		end = length
+	}
+
+	return
+}
+
+func kindString(n datamodel.Node) string {
+	if n == nil {
+		return "null"
+	}
+	return n.Kind().String()
+}
+
+type resolutionErr struct {
+	msg string
+	at  []string
+}
+
+func (r resolutionErr) Name() string {
+	return "ResolutionError"
+}
+
+func (r resolutionErr) Message() string {
+	return fmt.Sprintf("can not resolve path: .%s", strings.Join(r.at, "."))
+}
+
+func (r resolutionErr) At() []string {
+	return r.at
+}
+
+func (r resolutionErr) Error() string {
+	return r.Message()
+}
+
+func newResolutionError(message string, at []string) error {
+	return resolutionErr{message, at}
+}

pkg/policy/selector/selector_test.go

@@ -0,0 +1,413 @@
+package selector
+
+import (
+	"errors"
+	"math"
+	"strings"
+	"testing"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/codec/dagjson"
+	"github.com/ipld/go-ipld-prime/datamodel"
+	"github.com/ipld/go-ipld-prime/fluent/qp"
+	"github.com/ipld/go-ipld-prime/must"
+	basicnode "github.com/ipld/go-ipld-prime/node/basic"
+	"github.com/ipld/go-ipld-prime/node/bindnode"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSelect(t *testing.T) {
+	type name struct {
+		First  string
+		Middle *string
+		Last   string
+	}
+	type interest struct {
+		Name       string
+		Outdoor    bool
+		Experience int
+	}
+	type user struct {
+		Name          name
+		Age           int
+		Nationalities []string
+		Interests     []interest
+	}
+
+	ts, err := ipld.LoadSchemaBytes([]byte(`
+	  type User struct {
+		  name Name
+			age Int
+			nationalities [String]
+			interests [Interest]
+		}
+		type Name struct {
+			first String
+			middle optional String
+			last String
+		}
+		type Interest struct {
+			name String
+			outdoor Bool
+			experience Int
+		}
+	`))
+	require.NoError(t, err)
+	typ := ts.TypeByName("User")
+
+	am := "Joan"
+	alice := user{
+		Name:          name{First: "Alice", Middle: &am, Last: "Wonderland"},
+		Age:           24,
+		Nationalities: []string{"British"},
+		Interests: []interest{
+			{Name: "Cycling", Outdoor: true, Experience: 4},
+			{Name: "Chess", Outdoor: false, Experience: 2},
+		},
+	}
+	bob := user{
+		Name:          name{First: "Bob", Last: "Builder"},
+		Age:           35,
+		Nationalities: []string{"Canadian", "South African"},
+		Interests: []interest{
+			{Name: "Snowboarding", Outdoor: true, Experience: 8},
+			{Name: "Reading", Outdoor: false, Experience: 25},
+		},
+	}
+
+	anode := bindnode.Wrap(&alice, typ)
+	bnode := bindnode.Wrap(&bob, typ)
+
+	t.Run("identity", func(t *testing.T) {
+		sel, err := Parse(".")
+		require.NoError(t, err)
+
+		res, err := sel.Select(anode)
+		require.NoError(t, err)
+		require.NotEmpty(t, res)
+
+		age := must.Int(must.Node(res.LookupByString("age")))
+		require.Equal(t, int64(alice.Age), age)
+	})
+
+	t.Run("nested property", func(t *testing.T) {
+		sel, err := Parse(".name.first")
+		require.NoError(t, err)
+
+		res, err := sel.Select(anode)
+		require.NoError(t, err)
+		require.NotEmpty(t, res)
+
+		name := must.String(res)
+		require.Equal(t, alice.Name.First, name)
+
+		res, err = sel.Select(bnode)
+		require.NoError(t, err)
+		require.NotEmpty(t, res)
+
+		name = must.String(res)
+		require.Equal(t, bob.Name.First, name)
+	})
+
+	t.Run("optional nested property", func(t *testing.T) {
+		sel, err := Parse(".name.middle?")
+		require.NoError(t, err)
+
+		res, err := sel.Select(anode)
+		require.NoError(t, err)
+		require.NotEmpty(t, res)
+
+		name := must.String(res)
+		require.Equal(t, *alice.Name.Middle, name)
+
+		res, err = sel.Select(bnode)
+		require.NoError(t, err)
+		require.Empty(t, res)
+	})
+
+	t.Run("not exists", func(t *testing.T) {
+		sel, err := Parse(".name.foo")
+		require.NoError(t, err)
+
+		res, err := sel.Select(anode)
+		require.Error(t, err)
+		require.Empty(t, res)
+
+		require.ErrorAs(t, err, &resolutionErr{}, "error should be a resolution error")
+	})
+
+	t.Run("optional not exists", func(t *testing.T) {
+		sel, err := Parse(".name.foo?")
+		require.NoError(t, err)
+
+		one, err := sel.Select(anode)
+		require.NoError(t, err)
+		require.Empty(t, one)
+	})
+
+	t.Run("iterator", func(t *testing.T) {
+		sel, err := Parse(".interests[]")
+		require.NoError(t, err)
+
+		res, err := sel.Select(anode)
+		require.NoError(t, err)
+		require.NotEmpty(t, res)
+
+		iname := must.String(must.Node(must.Node(res.LookupByIndex(0)).LookupByString("name")))
+		require.Equal(t, alice.Interests[0].Name, iname)
+
+		iname = must.String(must.Node(must.Node(res.LookupByIndex(1)).LookupByString("name")))
+		require.Equal(t, alice.Interests[1].Name, iname)
+	})
+
+	t.Run("slice on string", func(t *testing.T) {
+		sel, err := Parse(`.[1:3]`)
+		require.NoError(t, err)
+
+		node := basicnode.NewString("hello")
+		res, err := sel.Select(node)
+		require.NoError(t, err)
+		require.NotEmpty(t, res)
+
+		str, err := res.AsString()
+		require.NoError(t, err)
+		require.Equal(t, "el", str) // assert sliced substring
+	})
+
+	t.Run("out of bounds slicing", func(t *testing.T) {
+		node, err := qp.BuildList(basicnode.Prototype.Any, 3, func(la datamodel.ListAssembler) {
+			qp.ListEntry(la, qp.Int(1))
+			qp.ListEntry(la, qp.Int(2))
+			qp.ListEntry(la, qp.Int(3))
+		})
+		require.NoError(t, err)
+
+		sel, err := Parse(`.[10:20]`)
+		require.NoError(t, err)
+
+		res, err := sel.Select(node)
+		require.NoError(t, err)
+		require.NotEmpty(t, res)
+		require.Equal(t, int64(0), res.Length())
+
+		_, err = res.LookupByIndex(0)
+		require.ErrorIs(t, err, datamodel.ErrNotExists{}) // assert empty result for out of bounds slice
+	})
+
+	t.Run("backward slicing", func(t *testing.T) {
+		node, err := qp.BuildList(basicnode.Prototype.Any, 3, func(la datamodel.ListAssembler) {
+			qp.ListEntry(la, qp.Int(1))
+			qp.ListEntry(la, qp.Int(2))
+			qp.ListEntry(la, qp.Int(3))
+		})
+		require.NoError(t, err)
+
+		sel, err := Parse(`.[5:2]`)
+		require.NoError(t, err)
+
+		res, err := sel.Select(node)
+		require.NoError(t, err)
+		require.NotEmpty(t, res)
+		require.Equal(t, int64(0), res.Length())
+
+		_, err = res.LookupByIndex(0)
+		require.ErrorIs(t, err, datamodel.ErrNotExists{}) // assert empty result for backward slice
+	})
+
+	t.Run("slice with negative index", func(t *testing.T) {
+		node, err := qp.BuildList(basicnode.Prototype.Any, 3, func(la datamodel.ListAssembler) {
+			qp.ListEntry(la, qp.Int(1))
+			qp.ListEntry(la, qp.Int(2))
+			qp.ListEntry(la, qp.Int(3))
+		})
+		require.NoError(t, err)
+
+		sel, err := Parse(`.[0:-1]`)
+		require.NoError(t, err)
+
+		res, err := sel.Select(node)
+		require.NoError(t, err)
+		require.NotEmpty(t, res)
+
+		val, err := res.LookupByIndex(1)
+		require.NoError(t, err)
+		require.Equal(t, 2, int(must.Int(val))) // Assert sliced value at index 1
+	})
+
+	t.Run("slice on bytes", func(t *testing.T) {
+		sel, err := Parse(`.[1:3]`)
+		require.NoError(t, err)
+
+		node := basicnode.NewBytes([]byte{0x01, 0x02, 0x03, 0x04, 0x05})
+		res, err := sel.Select(node)
+		require.NoError(t, err)
+		require.NotEmpty(t, res)
+
+		bytes, err := res.AsBytes()
+		require.NoError(t, err)
+		require.Equal(t, []byte{0x02, 0x03}, bytes) // assert sliced bytes
+	})
+
+	t.Run("index on bytes", func(t *testing.T) {
+		sel, err := Parse(`.[2]`)
+		require.NoError(t, err)
+
+		node := basicnode.NewBytes([]byte{0x01, 0x02, 0x03, 0x04, 0x05})
+		res, err := sel.Select(node)
+		require.NoError(t, err)
+		require.NotEmpty(t, res)
+
+		val, err := res.AsInt()
+		require.NoError(t, err)
+		require.Equal(t, int64(0x03), val) // assert indexed byte value
+	})
+
+	t.Run("out of bounds slicing on bytes", func(t *testing.T) {
+		sel, err := Parse(`.[10:20]`)
+		require.NoError(t, err)
+
+		node := basicnode.NewBytes([]byte{0x01, 0x02, 0x03})
+		res, err := sel.Select(node)
+		require.NoError(t, err)
+		require.NotNil(t, res)
+
+		bytes, err := res.AsBytes()
+		require.NoError(t, err)
+		require.Empty(t, bytes) // assert empty result for out of bounds slice
+	})
+
+	t.Run("out of bounds indexing on bytes", func(t *testing.T) {
+		sel, err := Parse(`.[10]`)
+		require.NoError(t, err)
+
+		node := basicnode.NewBytes([]byte{0x01, 0x02, 0x03})
+		_, err = sel.Select(node)
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "can not resolve path: .10") // assert error for out of bounds index
+	})
+}
+
+func FuzzParse(f *testing.F) {
+	selectorCorpus := []string{
+		`.`, `.[]`, `.[]?`, `.[][]?`, `.x`, `.["x"]`, `.[0]`, `.[-1]`, `.[0]`,
+		`.[0]`, `.[0:2]`, `.[1:]`, `.[:2]`, `.[0:2]`, `.[1:]`, `.x?`, `.x?`,
+		`.x?`, `.["x"]?`, `.length?`, `.[4]?`, `.[]`, `.[][]`, `.x`, `.x`, `.x`,
+		`.length`, `.[4]`,
+	}
+	for _, selector := range selectorCorpus {
+		f.Add(selector)
+	}
+	f.Fuzz(func(t *testing.T, selector string) {
+		// only look for panic()
+		_, _ = Parse(selector)
+	})
+}
+
+func FuzzParseAndSelect(f *testing.F) {
+	selectorCorpus := []string{
+		`.`, `.[]`, `.[]?`, `.[][]?`, `.x`, `.["x"]`, `.[0]`, `.[-1]`, `.[0]`,
+		`.[0]`, `.[0:2]`, `.[1:]`, `.[:2]`, `.[0:2]`, `.[1:]`, `.x?`, `.x?`,
+		`.x?`, `.["x"]?`, `.length?`, `.[4]?`, `.[]`, `.[][]`, `.x`, `.x`, `.x`,
+		`.length`, `.[4]`,
+	}
+	subjectCorpus := []string{
+		`{"x":1}`, `[1, 2]`, `null`, `[[1], 2, [3]]`, `{"x": 1 }`, `{"x": 1}`,
+		`[1, 2]`, `[1, 2]`, `"Hi"`, `{"/":{"bytes":"AAE"}`, `[0, 1, 2]`,
+		`[0, 1, 2]`, `[0, 1, 2]`, `"hello"`, `{"/":{"bytes":"AAEC"}}`, `{}`,
+		`null`, `[]`, `{}`, `[1, 2]`, `[0, 1]`, `null`, `[[1], 2, [3]]`, `{}`,
+		`null`, `[]`, `[1, 2]`, `[0, 1]`,
+	}
+	for i := 0; ; i++ {
+		switch {
+		case i < len(selectorCorpus) && i < len(subjectCorpus):
+			f.Add(selectorCorpus[i], subjectCorpus[i])
+			continue
+		case i > len(selectorCorpus):
+			f.Add("", subjectCorpus[i])
+			continue
+		case i > len(subjectCorpus):
+			f.Add(selectorCorpus[i], "")
+			continue
+		}
+		break
+	}
+
+	f.Fuzz(func(t *testing.T, selector, subject string) {
+		sel, err := Parse(selector)
+		if err != nil {
+			t.Skip()
+		}
+
+		np := basicnode.Prototype.Any
+		nb := np.NewBuilder()
+		err = dagjson.Decode(nb, strings.NewReader(subject))
+		if err != nil {
+			t.Skip()
+		}
+		node := nb.Build()
+		if node == nil {
+			t.Skip()
+		}
+
+		// look for panic()
+		_, err = sel.Select(node)
+		if err != nil && !errors.As(err, &resolutionErr{}) {
+			// not normal, we should only have resolution errors
+			t.Fatal(err)
+		}
+	})
+}
+
+func TestResolveSliceIndices(t *testing.T) {
+	tests := []struct {
+		name      string
+		slice     []int64
+		length    int64
+		wantStart int64
+		wantEnd   int64
+	}{
+		{
+			name:      "normal case",
+			slice:     []int64{1, 3},
+			length:    5,
+			wantStart: 1,
+			wantEnd:   3,
+		},
+		{
+			name:      "negative indices",
+			slice:     []int64{-2, -1},
+			length:    5,
+			wantStart: 3,
+			wantEnd:   4,
+		},
+		{
+			name:      "overflow protection negative start",
+			slice:     []int64{math.MinInt64, 3},
+			length:    5,
+			wantStart: 0,
+			wantEnd:   3,
+		},
+		{
+			name:      "overflow protection negative end",
+			slice:     []int64{0, math.MinInt64},
+			length:    5,
+			wantStart: 0,
+			wantEnd:   0,
+		},
+		{
+			name:      "max bounds",
+			slice:     []int64{0, math.MaxInt64},
+			length:    5,
+			wantStart: 0,
+			wantEnd:   5,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			start, end := resolveSliceIndices(tt.slice, tt.length)
+			require.Equal(t, tt.wantStart, start)
+			require.Equal(t, tt.wantEnd, end)
+		})
+	}
+}

pkg/policy/selector/supported_test.go

@@ -1,18 +1,15 @@
 package selector_test
 
 import (
-	"bytes"
 	"strings"
 	"testing"
 
 	"github.com/ipld/go-ipld-prime"
 	"github.com/ipld/go-ipld-prime/codec/dagjson"
-	"github.com/ipld/go-ipld-prime/datamodel"
 	basicnode "github.com/ipld/go-ipld-prime/node/basic"
-	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
-	"github.com/ucan-wg/go-ucan/v1/capability/policy/selector"
+	"github.com/ucan-wg/go-ucan/pkg/policy/selector"
 )
 
 // TestSupported Forms runs tests against the Selector according to the
@@ -26,18 +23,16 @@ func TestSupportedForms(t *testing.T) {
 		Output   string
 	}
 
-	// Pass
+	// Pass and return a node
 	for _, testcase := range []Testcase{
 		{Name: "Identity", Selector: `.`, Input: `{"x":1}`, Output: `{"x":1}`},
 		{Name: "Iterator", Selector: `.[]`, Input: `[1, 2]`, Output: `[1, 2]`},
-		{Name: "Optional Null Iterator", Selector: `.[]?`, Input: `null`, Output: `()`},
+		{Name: "Optional Null Iterator", Selector: `.[]?`, Input: `null`, Output: `[]`},
-		{Name: "Optional Iterator", Selector: `.[][]?`, Input: `[[1], 2, [3]]`, Output: `[1, 3]`},
 		{Name: "Object Key", Selector: `.x`, Input: `{"x": 1 }`, Output: `1`},
 		{Name: "Quoted Key", Selector: `.["x"]`, Input: `{"x": 1}`, Output: `1`},
 		{Name: "Index", Selector: `.[0]`, Input: `[1, 2]`, Output: `1`},
 		{Name: "Negative Index", Selector: `.[-1]`, Input: `[1, 2]`, Output: `2`},
-		{Name: "String Index", Selector: `.[0]`, Input: `"Hi"`, Output: `"H"`},
+		{Name: "Bytes Index", Selector: `.[0]`, Input: `{"/":{"bytes":"AAE"}}`, Output: `0`},
-		{Name: "Bytes Index", Selector: `.[0]`, Input: `{"/":{"bytes":"AAE"}`, Output: `0`},
 		{Name: "Array Slice", Selector: `.[0:2]`, Input: `[0, 1, 2]`, Output: `[0, 1]`},
 		{Name: "Array Slice", Selector: `.[1:]`, Input: `[0, 1, 2]`, Output: `[1, 2]`},
 		{Name: "Array Slice", Selector: `.[:2]`, Input: `[0, 1, 2]`, Output: `[0, 1]`},
@@ -52,35 +47,16 @@ func TestSupportedForms(t *testing.T) {
 			require.NoError(t, err)
 
 			// attempt to select
-			node, nodes, err := selector.Select(sel, makeNode(t, tc.Input))
+			res, err := sel.Select(makeNode(t, tc.Input))
 			require.NoError(t, err)
-			require.NotEqual(t, node != nil, len(nodes) > 0) // XOR (only one of node or nodes should be set)
+			require.NotNil(t, res)
-
-			// make an IPLD List node from a []datamodel.Node
-			if node == nil {
-				nb := basicnode.Prototype.List.NewBuilder()
-				la, err := nb.BeginList(int64(len(nodes)))
-				require.NoError(t, err)
-
-				for _, n := range nodes {
-					// TODO: This code is probably not needed if the Select operation properly prunes nil values - e.g.: Optional Iterator
-					if n == nil {
-						n = datamodel.Null
-					}
-
-					require.NoError(t, la.AssembleValue().AssignNode(n))
-				}
-				require.NoError(t, la.Finish())
-
-				node = nb.Build()
-			}
 
 			exp := makeNode(t, tc.Output)
-			equalIPLD(t, exp, node)
+			require.True(t, ipld.DeepEqual(exp, res))
 		})
 	}
 
-	// null
+	// No error and return null, as optional
 	for _, testcase := range []Testcase{
 		{Name: "Optional Missing Key", Selector: `.x?`, Input: `{}`},
 		{Name: "Optional Null Key", Selector: `.x?`, Input: `null`},
@@ -97,19 +73,15 @@ func TestSupportedForms(t *testing.T) {
 			require.NoError(t, err)
 
 			// attempt to select
-			node, nodes, err := selector.Select(sel, makeNode(t, tc.Input))
+			res, err := sel.Select(makeNode(t, tc.Input))
 			require.NoError(t, err)
-			// TODO: should Select return a single node which is sometimes a list or null?
+			require.Nil(t, res)
-			// require.Equal(t, datamodel.Null, node)
-			assert.Nil(t, node)
-			assert.Empty(t, nodes)
 		})
 	}
 
-	// error
+	// fail to select and return an error
 	for _, testcase := range []Testcase{
 		{Name: "Null Iterator", Selector: `.[]`, Input: `null`},
-		{Name: "Nested Iterator", Selector: `.[][]`, Input: `[[1], 2, [3]]`},
 		{Name: "Missing Key", Selector: `.x`, Input: `{}`},
 		{Name: "Null Key", Selector: `.x`, Input: `null`},
 		{Name: "Array Key", Selector: `.x`, Input: `[]`},
@@ -124,31 +96,13 @@ func TestSupportedForms(t *testing.T) {
 			require.NoError(t, err)
 
 			// attempt to select
-			node, nodes, err := selector.Select(sel, makeNode(t, tc.Input))
+			res, err := sel.Select(makeNode(t, tc.Input))
 			require.Error(t, err)
-			assert.Nil(t, node)
+			require.Nil(t, res)
-			assert.Empty(t, nodes)
 		})
 	}
 }
 
-func equalIPLD(t *testing.T, expected datamodel.Node, actual datamodel.Node) bool {
-	t.Helper()
-
-	exp, act := &bytes.Buffer{}, &bytes.Buffer{}
-	if err := dagjson.Encode(expected, exp); err != nil {
-		return assert.Fail(t, "Failed to encode json for expected IPLD node")
-	}
-
-	if err := dagjson.Encode(actual, act); err != nil {
-		return assert.Fail(t, "Failed to encode JSON for actual IPLD node")
-	}
-
-	require.JSONEq(t, exp.String(), act.String())
-
-	return true
-}
-
 func makeNode(t *testing.T, dagJsonInput string) ipld.Node {
 	t.Helper()
 

pkg/secretbox/secretbox.go

@@ -0,0 +1,90 @@
+package secretbox
+
+import (
+	"crypto/rand"
+	"errors"
+	"fmt"
+	"io"
+
+	"golang.org/x/crypto/nacl/secretbox"
+)
+
+const keySize = 32 // secretbox allows only 32-byte keys
+
+var ErrShortCipherText = errors.New("ciphertext too short")
+var ErrNoEncryptionKey = errors.New("encryption key is required")
+var ErrInvalidKeySize = errors.New("invalid key size: must be 32 bytes")
+var ErrZeroKey = errors.New("encryption key cannot be all zeros")
+
+// GenerateKey generates a random 32-byte key to be used by EncryptWithKey and DecryptWithKey
+func GenerateKey() ([]byte, error) {
+	key := make([]byte, keySize)
+	if _, err := io.ReadFull(rand.Reader, key); err != nil {
+		return nil, fmt.Errorf("failed to generate key: %w", err)
+	}
+	return key, nil
+}
+
+// EncryptWithKey encrypts data using NaCl's secretbox with the provided key.
+// 40 bytes of overhead (24-byte nonce + 16-byte MAC) are added to the plaintext size.
+func EncryptWithKey(data, key []byte) ([]byte, error) {
+	if err := validateKey(key); err != nil {
+		return nil, err
+	}
+
+	var secretKey [keySize]byte
+	copy(secretKey[:], key)
+
+	// Generate 24 bytes of random data as nonce
+	var nonce [24]byte
+	if _, err := io.ReadFull(rand.Reader, nonce[:]); err != nil {
+		return nil, err
+	}
+
+	// Encrypt and authenticate data
+	encrypted := secretbox.Seal(nonce[:], data, &nonce, &secretKey)
+	return encrypted, nil
+}
+
+// DecryptStringWithKey decrypts data using secretbox with the provided key
+func DecryptStringWithKey(data, key []byte) ([]byte, error) {
+	if err := validateKey(key); err != nil {
+		return nil, err
+	}
+
+	if len(data) < 24 {
+		return nil, ErrShortCipherText
+	}
+
+	var secretKey [keySize]byte
+	copy(secretKey[:], key)
+
+	var nonce [24]byte
+	copy(nonce[:], data[:24])
+
+	decrypted, ok := secretbox.Open(nil, data[24:], &nonce, &secretKey)
+	if !ok {
+		return nil, errors.New("decryption failed")
+	}
+
+	return decrypted, nil
+}
+
+func validateKey(key []byte) error {
+	if key == nil {
+		return ErrNoEncryptionKey
+	}
+
+	if len(key) != keySize {
+		return ErrInvalidKeySize
+	}
+
+	// check if key is all zeros
+	for _, b := range key {
+		if b != 0 {
+			return nil
+		}
+	}
+
+	return ErrZeroKey
+}

pkg/secretbox/secretbox_test.go

@@ -0,0 +1,144 @@
+package secretbox
+
+import (
+	"bytes"
+	"crypto/rand"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestSecretBoxEncryption(t *testing.T) {
+	t.Parallel()
+
+	key := make([]byte, keySize) // generate random 32-byte key
+	_, errKey := rand.Read(key)
+	require.NoError(t, errKey)
+
+	tests := []struct {
+		name    string
+		data    []byte
+		key     []byte
+		wantErr error
+	}{
+		{
+			name: "valid encryption/decryption",
+			data: []byte("hello world"),
+			key:  key,
+		},
+		{
+			name:    "nil key returns error",
+			data:    []byte("hello world"),
+			key:     nil,
+			wantErr: ErrNoEncryptionKey,
+		},
+		{
+			name: "empty data",
+			data: []byte{},
+			key:  key,
+		},
+		{
+			name:    "invalid key size",
+			data:    []byte("hello world"),
+			key:     make([]byte, 16), // Only 32 bytes allowed now
+			wantErr: ErrInvalidKeySize,
+		},
+		{
+			name:    "zero key returns error",
+			data:    []byte("hello world"),
+			key:     make([]byte, keySize),
+			wantErr: ErrZeroKey,
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			encrypted, err := EncryptWithKey(tt.data, tt.key)
+			if tt.wantErr != nil {
+				require.ErrorIs(t, err, tt.wantErr)
+				return
+			}
+			require.NoError(t, err)
+
+			// Verify encrypted data is different and includes nonce
+			require.Greater(t, len(encrypted), 24) // At least nonce size
+			if len(tt.data) > 0 {
+				require.NotEqual(t, tt.data, encrypted[24:]) // Ignore nonce prefix
+			}
+
+			decrypted, err := DecryptStringWithKey(encrypted, tt.key)
+			require.NoError(t, err)
+			require.True(t, bytes.Equal(tt.data, decrypted))
+		})
+	}
+}
+
+func TestDecryptionErrors(t *testing.T) {
+	t.Parallel()
+
+	key := make([]byte, keySize)
+	_, err := rand.Read(key)
+	require.NoError(t, err)
+
+	// Create valid encrypted data for tampering tests
+	validData := []byte("test message")
+	encrypted, err := EncryptWithKey(validData, key)
+	require.NoError(t, err)
+
+	tests := []struct {
+		name   string
+		data   []byte
+		key    []byte
+		errMsg string
+	}{
+		{
+			name:   "short ciphertext",
+			data:   make([]byte, 23), // Less than nonce size
+			key:    key,
+			errMsg: "ciphertext too short",
+		},
+		{
+			name:   "invalid ciphertext",
+			data:   make([]byte, 24), // Just nonce size
+			key:    key,
+			errMsg: "decryption failed",
+		},
+		{
+			name:   "tampered ciphertext",
+			data:   tamperWithBytes(encrypted),
+			key:    key,
+			errMsg: "decryption failed",
+		},
+		{
+			name:   "missing key",
+			data:   encrypted,
+			key:    nil,
+			errMsg: "encryption key is required",
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			_, err := DecryptStringWithKey(tt.data, tt.key)
+			require.Error(t, err)
+			require.Contains(t, err.Error(), tt.errMsg)
+		})
+	}
+}
+
+// tamperWithBytes modifies a byte in the encrypted data to simulate tampering
+func tamperWithBytes(data []byte) []byte {
+	if len(data) < 25 { // Need at least nonce + 1 byte
+		return data
+	}
+	tampered := make([]byte, len(data))
+	copy(tampered, data)
+	tampered[24] ^= 0x01 // Modify first byte after nonce
+	return tampered
+}

token/attestation/attestation.go

@@ -0,0 +1,210 @@
+// Package attestation implements the UCAN [attestation] specification with
+// an immutable Token type as well as methods to convert the Token to and
+// from the [envelope]-enclosed, signed and DAG-CBOR-encoded form that
+// should most commonly be used for transport and storage.
+//
+// [envelope]: https://github.com/ucan-wg/spec#envelope
+// [attestation]: TBD
+package attestation
+
+import (
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/MetaMask/go-did-it"
+
+	"github.com/ucan-wg/go-ucan/pkg/claims"
+	"github.com/ucan-wg/go-ucan/pkg/meta"
+	"github.com/ucan-wg/go-ucan/token/internal/nonce"
+	"github.com/ucan-wg/go-ucan/token/internal/parse"
+)
+
+// Token is an immutable type that holds the fields of a UCAN attestation.
+type Token struct {
+	// The DID of the Invoker
+	issuer did.DID
+	// TODO: should this exist?
+	// audience did.DID
+
+	// Arbitrary Claims
+	claims *claims.Claims
+
+	// Arbitrary Metadata
+	meta *meta.Meta
+
+	// A unique, random nonce
+	nonce []byte
+	// The timestamp at which the Invocation becomes invalid
+	expiration *time.Time
+	// The timestamp at which the Invocation was created
+	issuedAt *time.Time
+}
+
+// New creates an attestation Token with the provided options.
+//
+// If no nonce is provided, a random 12-byte nonce is generated. Use the
+// WithNonce or WithEmptyNonce options to specify provide your own nonce
+// or to leave the nonce empty respectively.
+//
+// If no IssuedAt is provided, the current time is used. Use the
+// IssuedAt or WithIssuedAtIn Options to specify a different time
+// or the WithoutIssuedAt Option to clear the Token's IssuedAt field.
+//
+// With the exception of the WithMeta option, all others will overwrite
+// the previous contents of their target field.
+//
+// You can read it as "(Issuer - I) attest (arbitrary claim)".
+func New(iss did.DID, opts ...Option) (*Token, error) {
+	iat := time.Now()
+
+	tkn := Token{
+		issuer:   iss,
+		claims:   claims.NewClaims(),
+		meta:     meta.NewMeta(),
+		nonce:    nil,
+		issuedAt: &iat,
+	}
+
+	for _, opt := range opts {
+		if err := opt(&tkn); err != nil {
+			return nil, err
+		}
+	}
+
+	var err error
+	if len(tkn.nonce) == 0 {
+		tkn.nonce, err = nonce.Generate()
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if err := tkn.validate(); err != nil {
+		return nil, err
+	}
+
+	return &tkn, nil
+}
+
+// Issuer returns the did.DID representing the Token's issuer.
+func (t *Token) Issuer() did.DID {
+	return t.issuer
+}
+
+// Claims returns the Token's claims.
+func (t *Token) Claims() claims.ReadOnly {
+	return t.claims.ReadOnly()
+}
+
+// Meta returns the Token's metadata.
+func (t *Token) Meta() meta.ReadOnly {
+	return t.meta.ReadOnly()
+}
+
+// Nonce returns the random Nonce encapsulated in this Token.
+func (t *Token) Nonce() []byte {
+	return t.nonce
+}
+
+// Expiration returns the time at which the Token expires.
+func (t *Token) Expiration() *time.Time {
+	return t.expiration
+}
+
+// IssuedAt returns the time.Time at which the invocation token was
+// created.
+func (t *Token) IssuedAt() *time.Time {
+	return t.issuedAt
+}
+
+// IsValidNow verifies that the token can be used at the current time, based on expiration or "not before" fields.
+// This does NOT do any other kind of verifications.
+func (t *Token) IsValidNow() bool {
+	return t.IsValidAt(time.Now())
+}
+
+// IsValidAt verifies that the token can be used at the given time, based on expiration or "not before" fields.
+// This does NOT do any other kind of verifications.
+func (t *Token) IsValidAt(ti time.Time) bool {
+	if t.expiration != nil && ti.After(*t.expiration) {
+		return false
+	}
+	return true
+}
+
+func (t *Token) String() string {
+	var res strings.Builder
+
+	res.WriteString(fmt.Sprintf("Issuer: %s\n", t.Issuer()))
+	res.WriteString(fmt.Sprintf("Nonce: %s\n", base64.StdEncoding.EncodeToString(t.Nonce())))
+	res.WriteString(fmt.Sprintf("Meta: %s\n", t.Meta()))
+	res.WriteString(fmt.Sprintf("Expiration: %v\n", t.Expiration()))
+	res.WriteString(fmt.Sprintf("Issued At: %v\n", t.IssuedAt()))
+
+	return res.String()
+}
+
+func (t *Token) validate() error {
+	var errs error
+
+	requiredDID := func(id did.DID, fieldname string) {
+		if id == nil {
+			errs = errors.Join(errs, fmt.Errorf(`a valid did is required for %s: %s`, fieldname, id.String()))
+		}
+	}
+
+	requiredDID(t.issuer, "Issuer")
+
+	if len(t.nonce) < 12 {
+		errs = errors.Join(errs, fmt.Errorf("token nonce too small"))
+	}
+
+	return errs
+}
+
+// tokenFromModel build a decoded view of the raw IPLD data.
+// This function also serves as validation.
+func tokenFromModel(m tokenPayloadModel) (*Token, error) {
+	var (
+		tkn Token
+		err error
+	)
+
+	if tkn.issuer, err = did.Parse(m.Iss); err != nil {
+		return nil, fmt.Errorf("parse iss: %w", err)
+	}
+
+	tkn.claims = m.Claims
+	if tkn.claims == nil {
+		tkn.claims = claims.NewClaims()
+	}
+
+	tkn.meta = m.Meta
+	if tkn.meta == nil {
+		tkn.meta = meta.NewMeta()
+	}
+
+	if len(m.Nonce) == 0 {
+		return nil, fmt.Errorf("nonce is required")
+	}
+	tkn.nonce = m.Nonce
+
+	tkn.expiration, err = parse.OptionalTimestamp(m.Exp)
+	if err != nil {
+		return nil, fmt.Errorf("parse expiration: %w", err)
+	}
+
+	tkn.issuedAt, err = parse.OptionalTimestamp(m.Iat)
+	if err != nil {
+		return nil, fmt.Errorf("parse IssuedAt: %w", err)
+	}
+
+	if err := tkn.validate(); err != nil {
+		return nil, err
+	}
+
+	return &tkn, nil
+}

token/attestation/attestation.ipldsch

@@ -0,0 +1,22 @@
+type DID string
+
+# The Attestation payload
+type Payload struct {
+    # Issuer DID (sender)
+    iss DID
+    # Audience DID (receiver) TODO: should that exist?
+    # aud DID
+
+    # Arbitrary claims
+    claims optional {String: Any}
+
+    # Arbitrary Metadata
+    meta optional {String : Any}
+
+    # A unique, random nonce
+    nonce Bytes
+    # The timestamp at which the Invocation becomes invalid
+    exp nullable Int
+    # The Timestamp at which the Invocation was created
+    iat optional Int
+}

token/attestation/examples_test.go

@@ -0,0 +1,132 @@
+package attestation_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/MetaMask/go-did-it"
+	didkeyctl "github.com/MetaMask/go-did-it/controller/did-key"
+	"github.com/MetaMask/go-did-it/crypto/ed25519"
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/codec/dagcbor"
+	"github.com/ipld/go-ipld-prime/codec/dagjson"
+	"github.com/ipld/go-ipld-prime/node/basicnode"
+
+	"github.com/ucan-wg/go-ucan/token/attestation"
+)
+
+func ExampleNew() {
+	privKey, iss, _, _, err := setupExampleNew()
+	if err != nil {
+		fmt.Println("failed to create setup:", err.Error())
+		return
+	}
+
+	att, err := attestation.New(iss,
+		attestation.WithClaim("claim1", "UCAN is great"),
+		attestation.WithMeta("env", "development"),
+		attestation.WithExpirationIn(time.Minute),
+		attestation.WithoutIssuedAt())
+	if err != nil {
+		fmt.Println("failed to create attestation:", err.Error())
+		return
+	}
+
+	// foo, _ := att.ToDagJson(privKey)
+	// os.WriteFile("testdata/new.dagjson", foo, 0666)
+	// fmt.Println(base64.StdEncoding.EncodeToString(privKey.ToBytes()))
+
+	data, cid, err := att.ToSealed(privKey)
+	if err != nil {
+		fmt.Println("failed to seal attestation:", err.Error())
+		return
+	}
+
+	json, err := prettyDAGJSON(data)
+	if err != nil {
+		fmt.Println("failed to pretty DAG-JSON:", err.Error())
+		return
+	}
+
+	fmt.Println("CID:", cid)
+	fmt.Println("Token (pretty DAG-JSON):")
+	fmt.Println(json)
+
+	// Expected CID and DAG-JSON output:
+	// CID: bafyreibm5vo6gk75oreefkg6xkrrfb4d5dgkccgmutirjgtzi5j45svjm4
+	// Token (pretty DAG-JSON):
+	// [
+	//  {
+	//    "/": {
+	//      "bytes": "ApuXUsUYhqostO2zfKZK50GW0gXYPtrlpoVA8EwGFdyYahQecOizVpl+9wy64aqk2rMP4Q0UEUKCTV0ONMdPAw"
+	//    }
+	//  },
+	//  {
+	//    "h": {
+	//      "/": {
+	//        "bytes": "NAHtAe0BE3E"
+	//      }
+	//    },
+	//    "ucan/att@tbd": {
+	//      "claims": {
+	//        "claim1": "UCAN is great"
+	//      },
+	//      "exp": 1767790971,
+	//      "iss": "did:key:z6Mkm4RzzBDfSHqmwV9dp5jFsLkVgKRYp1PhSj7VybCcLHC4",
+	//      "meta": {
+	//        "env": "development"
+	//      },
+	//      "nonce": {
+	//        "/": {
+	//          "bytes": "NjS8QPvft97jbtUG"
+	//        }
+	//      }
+	//    }
+	//  }
+	// ]
+}
+
+func prettyDAGJSON(data []byte) (string, error) {
+	var node ipld.Node
+
+	node, err := ipld.Decode(data, dagcbor.Decode)
+	if err != nil {
+		return "", err
+	}
+
+	jsonData, err := ipld.Encode(node, dagjson.Encode)
+	if err != nil {
+		return "", err
+	}
+
+	var out bytes.Buffer
+	if err := json.Indent(&out, jsonData, "", "  "); err != nil {
+		return "", err
+	}
+
+	return out.String(), nil
+}
+
+func setupExampleNew() (privKey ed25519.PrivateKey, iss did.DID, claims map[string]any, meta map[string]any, errs error) {
+	var err error
+
+	_, privKey, err = ed25519.GenerateKeyPair()
+	if err != nil {
+		errs = errors.Join(errs, fmt.Errorf("failed to generate Ed25519 keypair: %w", err))
+		return
+	}
+	iss = didkeyctl.FromPrivateKey(privKey)
+
+	claims = map[string]any{
+		"claim1": "UCAN is great",
+	}
+
+	meta = map[string]any{
+		"env": basicnode.NewString("development"),
+	}
+
+	return // WARNING: named return values
+}

token/attestation/ipld.go

@@ -0,0 +1,227 @@
+package attestation
+
+import (
+	"io"
+
+	"github.com/MetaMask/go-did-it"
+	"github.com/MetaMask/go-did-it/crypto"
+	"github.com/ipfs/go-cid"
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/codec"
+	"github.com/ipld/go-ipld-prime/codec/dagcbor"
+	"github.com/ipld/go-ipld-prime/codec/dagjson"
+	"github.com/ipld/go-ipld-prime/datamodel"
+
+	"github.com/ucan-wg/go-ucan/token/internal/envelope"
+)
+
+// ToSealed wraps the attestation token in an envelope, generates the
+// signature, encodes the result to DAG-CBOR and calculates the CID of
+// the resulting binary data.
+func (t *Token) ToSealed(privKey crypto.PrivateKeySigningBytes) ([]byte, cid.Cid, error) {
+	data, err := t.ToDagCbor(privKey)
+	if err != nil {
+		return nil, cid.Undef, err
+	}
+
+	id, err := envelope.CIDFromBytes(data)
+	if err != nil {
+		return nil, cid.Undef, err
+	}
+
+	return data, id, nil
+}
+
+// ToSealedWriter is the same as ToSealed but accepts an io.Writer.
+func (t *Token) ToSealedWriter(w io.Writer, privKey crypto.PrivateKeySigningBytes) (cid.Cid, error) {
+	cidWriter := envelope.NewCIDWriter(w)
+
+	if err := t.ToDagCborWriter(cidWriter, privKey); err != nil {
+		return cid.Undef, err
+	}
+
+	return cidWriter.CID()
+}
+
+// FromSealed decodes the provided binary data from the DAG-CBOR format,
+// verifies that the envelope's signature is correct based on the public
+// key taken from the issuer (iss) field and calculates the CID of the
+// incoming data.
+func FromSealed(data []byte, resolvOpts ...did.ResolutionOption) (*Token, cid.Cid, error) {
+	tkn, err := FromDagCbor(data, resolvOpts...)
+	if err != nil {
+		return nil, cid.Undef, err
+	}
+
+	id, err := envelope.CIDFromBytes(data)
+	if err != nil {
+		return nil, cid.Undef, err
+	}
+
+	return tkn, id, nil
+}
+
+// FromSealedReader is the same as Unseal but accepts an io.Reader.
+func FromSealedReader(r io.Reader, resolvOpts ...did.ResolutionOption) (*Token, cid.Cid, error) {
+	cidReader := envelope.NewCIDReader(r)
+
+	tkn, err := FromDagCborReader(cidReader, resolvOpts...)
+	if err != nil {
+		return nil, cid.Undef, err
+	}
+
+	id, err := cidReader.CID()
+	if err != nil {
+		return nil, cid.Undef, err
+	}
+
+	return tkn, id, nil
+}
+
+// Encode marshals a Token to the format specified by the provided
+// codec.Encoder.
+func (t *Token) Encode(privKey crypto.PrivateKeySigningBytes, encFn codec.Encoder) ([]byte, error) {
+	node, err := t.toIPLD(privKey)
+	if err != nil {
+		return nil, err
+	}
+
+	return ipld.Encode(node, encFn)
+}
+
+// EncodeWriter is the same as Encode, but accepts an io.Writer.
+func (t *Token) EncodeWriter(w io.Writer, privKey crypto.PrivateKeySigningBytes, encFn codec.Encoder) error {
+	node, err := t.toIPLD(privKey)
+	if err != nil {
+		return err
+	}
+
+	return ipld.EncodeStreaming(w, node, encFn)
+}
+
+// ToDagCbor marshals the Token to the DAG-CBOR format.
+func (t *Token) ToDagCbor(privKey crypto.PrivateKeySigningBytes) ([]byte, error) {
+	return t.Encode(privKey, dagcbor.Encode)
+}
+
+// ToDagCborWriter is the same as ToDagCbor, but it accepts an io.Writer.
+func (t *Token) ToDagCborWriter(w io.Writer, privKey crypto.PrivateKeySigningBytes) error {
+	return t.EncodeWriter(w, privKey, dagcbor.Encode)
+}
+
+// ToDagJson marshals the Token to the DAG-JSON format.
+func (t *Token) ToDagJson(privKey crypto.PrivateKeySigningBytes) ([]byte, error) {
+	return t.Encode(privKey, dagjson.Encode)
+}
+
+// ToDagJsonWriter is the same as ToDagJson, but it accepts an io.Writer.
+func (t *Token) ToDagJsonWriter(w io.Writer, privKey crypto.PrivateKeySigningBytes) error {
+	return t.EncodeWriter(w, privKey, dagjson.Encode)
+}
+
+// Decode unmarshals the input data using the format specified by the
+// provided codec.Decoder into a Token.
+//
+// An error is returned if the conversion fails or if the resulting
+// Token is invalid.
+func Decode(b []byte, decFn codec.Decoder, resolvOpts ...did.ResolutionOption) (*Token, error) {
+	node, err := ipld.Decode(b, decFn)
+	if err != nil {
+		return nil, err
+	}
+	return FromIPLD(node, resolvOpts...)
+}
+
+// DecodeReader is the same as Decode, but accept an io.Reader.
+func DecodeReader(r io.Reader, decFn codec.Decoder, resolvOpts ...did.ResolutionOption) (*Token, error) {
+	node, err := ipld.DecodeStreaming(r, decFn)
+	if err != nil {
+		return nil, err
+	}
+	return FromIPLD(node, resolvOpts...)
+}
+
+// FromDagCbor unmarshals the input data into a Token.
+//
+// An error is returned if the conversion fails or if the resulting
+// Token is invalid.
+func FromDagCbor(data []byte, resolvOpts ...did.ResolutionOption) (*Token, error) {
+	pay, err := envelope.FromDagCbor[*tokenPayloadModel](data, resolvOpts...)
+	if err != nil {
+		return nil, err
+	}
+
+	tkn, err := tokenFromModel(*pay)
+	if err != nil {
+		return nil, err
+	}
+
+	return tkn, err
+}
+
+// FromDagCborReader is the same as FromDagCbor, but accept an io.Reader.
+func FromDagCborReader(r io.Reader, resolvOpts ...did.ResolutionOption) (*Token, error) {
+	return DecodeReader(r, dagcbor.Decode, resolvOpts...)
+}
+
+// FromDagJson unmarshals the input data into a Token.
+//
+// An error is returned if the conversion fails or if the resulting
+// Token is invalid.
+func FromDagJson(data []byte, resolvOpts ...did.ResolutionOption) (*Token, error) {
+	return Decode(data, dagjson.Decode, resolvOpts...)
+}
+
+// FromDagJsonReader is the same as FromDagJson, but accept an io.Reader.
+func FromDagJsonReader(r io.Reader, resolvOpts ...did.ResolutionOption) (*Token, error) {
+	return DecodeReader(r, dagjson.Decode, resolvOpts...)
+}
+
+// FromIPLD decode the given IPLD representation into a Token.
+func FromIPLD(node datamodel.Node, resolvOpts ...did.ResolutionOption) (*Token, error) {
+	pay, err := envelope.FromIPLD[*tokenPayloadModel](node, resolvOpts...)
+	if err != nil {
+		return nil, err
+	}
+
+	tkn, err := tokenFromModel(*pay)
+	if err != nil {
+		return nil, err
+	}
+
+	return tkn, err
+}
+
+func (t *Token) toIPLD(privKey crypto.PrivateKeySigningBytes) (datamodel.Node, error) {
+	var exp *int64
+	if t.expiration != nil {
+		u := t.expiration.Unix()
+		exp = &u
+	}
+
+	var iat *int64
+	if t.issuedAt != nil {
+		i := t.issuedAt.Unix()
+		iat = &i
+	}
+
+	model := &tokenPayloadModel{
+		Iss:    t.issuer.String(),
+		Claims: t.claims,
+		Meta:   t.meta,
+		Nonce:  t.nonce,
+		Exp:    exp,
+		Iat:    iat,
+	}
+
+	if len(model.Claims.Keys) == 0 {
+		model.Claims = nil
+	}
+
+	// seems like it's a requirement to have a null meta if there are no values?
+	if len(model.Meta.Keys) == 0 {
+		model.Meta = nil
+	}
+
+	return envelope.ToIPLD(privKey, model)
+}

token/attestation/ipld_test.go

@@ -0,0 +1,35 @@
+package attestation_test
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/ucan-wg/go-ucan/token/attestation"
+)
+
+func TestSealUnsealRoundtrip(t *testing.T) {
+	t.Parallel()
+
+	privKey, iss, claims, meta, err := setupExampleNew()
+	require.NoError(t, err)
+
+	tkn1, err := attestation.New(iss,
+		attestation.WithClaimMap(claims),
+		attestation.WithMetaMap(meta),
+		attestation.WithExpirationIn(time.Minute),
+		attestation.WithoutIssuedAt(),
+	)
+	require.NoError(t, err)
+
+	data, cid1, err := tkn1.ToSealed(privKey)
+	require.NoError(t, err)
+
+	tkn2, cid2, err := attestation.FromSealed(data)
+	require.NoError(t, err)
+
+	assert.Equal(t, cid1, cid2)
+	assert.Equal(t, tkn1, tkn2)
+}

token/attestation/options.go

@@ -0,0 +1,168 @@
+package attestation
+
+import (
+	"time"
+)
+
+// Option is a type that allows optional fields to be set during the
+// creation of a Token.
+type Option func(*Token) error
+
+// WithClaim adds a key/value pair in the "claims" field.
+//
+// WithClaims can be used multiple times in the same call.
+// Accepted types for the value are: bool, string, int, int32, int64, []byte,
+// and ipld.Node.
+func WithClaim(key string, val any) Option {
+	return func(t *Token) error {
+		return t.claims.Add(key, val)
+	}
+}
+
+// WithClaimsMap adds all key/value pairs in the provided map to the
+// Token's "claims" field.
+//
+// WithClaimsMap can be used multiple times in the same call.
+// Accepted types for the value are: bool, string, int, int32, int64, []byte,
+// and ipld.Node.
+func WithClaimMap(m map[string]any) Option {
+	return func(t *Token) error {
+		for k, v := range m {
+			if err := t.claims.Add(k, v); err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+}
+
+// WithEncryptedClaimsString adds a key/value pair in the "claims" field.
+// The string value is encrypted with the given aesKey.
+func WithEncryptedClaimsString(key, val string, encryptionKey []byte) Option {
+	return func(t *Token) error {
+		return t.claims.AddEncrypted(key, val, encryptionKey)
+	}
+}
+
+// WithEncryptedClaimsBytes adds a key/value pair in the "claims" field.
+// The []byte value is encrypted with the given aesKey.
+func WithEncryptedClaimsBytes(key string, val, encryptionKey []byte) Option {
+	return func(t *Token) error {
+		return t.claims.AddEncrypted(key, val, encryptionKey)
+	}
+}
+
+// WithMeta adds a key/value pair in the "meta" field.
+//
+// WithMeta can be used multiple times in the same call.
+// Accepted types for the value are: bool, string, int, int32, int64, []byte,
+// and ipld.Node.
+func WithMeta(key string, val any) Option {
+	return func(t *Token) error {
+		return t.meta.Add(key, val)
+	}
+}
+
+// WithMetaMap adds all key/value pairs in the provided map to the
+// Token's "meta" field.
+//
+// WithMetaMap can be used multiple times in the same call.
+// Accepted types for the value are: bool, string, int, int32, int64, []byte,
+// and ipld.Node.
+func WithMetaMap(m map[string]any) Option {
+	return func(t *Token) error {
+		for k, v := range m {
+			if err := t.meta.Add(k, v); err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+}
+
+// WithEncryptedMetaString adds a key/value pair in the "meta" field.
+// The string value is encrypted with the given aesKey.
+func WithEncryptedMetaString(key, val string, encryptionKey []byte) Option {
+	return func(t *Token) error {
+		return t.meta.AddEncrypted(key, val, encryptionKey)
+	}
+}
+
+// WithEncryptedMetaBytes adds a key/value pair in the "meta" field.
+// The []byte value is encrypted with the given aesKey.
+func WithEncryptedMetaBytes(key string, val, encryptionKey []byte) Option {
+	return func(t *Token) error {
+		return t.meta.AddEncrypted(key, val, encryptionKey)
+	}
+}
+
+// WithNonce sets the Token's nonce with the given value.
+//
+// If this option is not used, a random 12-byte nonce is generated for
+// this required field.  If you truly want to create an invocation Token
+// without a nonce, use the WithEmptyNonce Option which will set the
+// nonce to an empty byte array.
+func WithNonce(nonce []byte) Option {
+	return func(t *Token) error {
+		t.nonce = nonce
+
+		return nil
+	}
+}
+
+// WithEmptyNonce sets the Token's nonce to an empty byte slice as
+// suggested by the UCAN spec for invocation tokens that represent
+// idempotent operations.
+func WithEmptyNonce() Option {
+	return func(t *Token) error {
+		t.nonce = []byte{}
+
+		return nil
+	}
+}
+
+// WithExpiration set's the Token's optional "expiration" field to the
+// value of the provided time.Time.
+func WithExpiration(exp time.Time) Option {
+	return func(t *Token) error {
+		exp = exp.Round(time.Second)
+		t.expiration = &exp
+
+		return nil
+	}
+}
+
+// WithExpirationIn set's the Token's optional "expiration" field to
+// Now() plus the given duration.
+func WithExpirationIn(after time.Duration) Option {
+	return WithExpiration(time.Now().Add(after))
+}
+
+// WithIssuedAt sets the Token's IssuedAt field to the provided
+// time.Time.
+//
+// If this Option is not provided, the invocation Token's iat field will
+// be set to the value of time.Now().  If you want to create an invocation
+// Token without this field being set, use the WithoutIssuedAt Option.
+func WithIssuedAt(iat time.Time) Option {
+	return func(t *Token) error {
+		t.issuedAt = &iat
+
+		return nil
+	}
+}
+
+// WithIssuedAtIn sets the Token's IssuedAt field to Now() plus the
+// given duration.
+func WithIssuedAtIn(after time.Duration) Option {
+	return WithIssuedAt(time.Now().Add(after))
+}
+
+// WithoutIssuedAt clears the Token's IssuedAt field.
+func WithoutIssuedAt() Option {
+	return func(t *Token) error {
+		t.issuedAt = nil
+
+		return nil
+	}
+}

token/attestation/schema.go

@@ -0,0 +1,73 @@
+package attestation
+
+import (
+	_ "embed"
+	"fmt"
+	"sync"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/node/bindnode"
+	"github.com/ipld/go-ipld-prime/schema"
+
+	"github.com/ucan-wg/go-ucan/pkg/claims"
+	"github.com/ucan-wg/go-ucan/pkg/meta"
+	"github.com/ucan-wg/go-ucan/token/internal/envelope"
+)
+
+// [Tag] is the string used as a key within the SigPayload that identifies
+// that the TokenPayload is an attestation.
+//
+// [Tag]: TODO: TBD
+const Tag = "ucan/att@tbd" // TODO: TBD
+
+//go:embed attestation.ipldsch
+var schemaBytes []byte
+
+var (
+	once      sync.Once
+	ts        *schema.TypeSystem
+	errSchema error
+)
+
+func mustLoadSchema() *schema.TypeSystem {
+	once.Do(func() {
+		ts, errSchema = ipld.LoadSchemaBytes(schemaBytes)
+	})
+	if errSchema != nil {
+		panic(fmt.Errorf("failed to load IPLD schema: %s", errSchema))
+	}
+	return ts
+}
+
+func payloadType() schema.Type {
+	return mustLoadSchema().TypeByName("Payload")
+}
+
+var _ envelope.Tokener = (*tokenPayloadModel)(nil)
+
+type tokenPayloadModel struct {
+	// The DID of the Invoker
+	Iss string
+
+	// Arbitrary claims
+	Claims *claims.Claims
+
+	// Arbitrary Metadata
+	Meta *meta.Meta
+
+	// A unique, random nonce
+	Nonce []byte
+	// The timestamp at which the Invocation becomes invalid
+	// optional: can be nil
+	Exp *int64
+	// The timestamp at which the Invocation was created
+	Iat *int64
+}
+
+func (e *tokenPayloadModel) Prototype() schema.TypedPrototype {
+	return bindnode.Prototype((*tokenPayloadModel)(nil), payloadType())
+}
+
+func (*tokenPayloadModel) Tag() string {
+	return Tag
+}

token/attestation/schema_test.go

@@ -0,0 +1,89 @@
+package attestation_test
+
+import (
+	"bytes"
+	_ "embed"
+	"encoding/base64"
+	"testing"
+
+	"github.com/MetaMask/go-did-it/crypto"
+	"github.com/MetaMask/go-did-it/crypto/ed25519"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/ucan-wg/go-ucan/token/attestation"
+	"github.com/ucan-wg/go-ucan/token/internal/envelope"
+)
+
+//go:embed testdata/new.dagjson
+var newDagJson []byte
+
+const (
+	issuerPrivKeyCfg = "8bX3+HJxxlIGgNZ8yFG+t48oMGygEGyWD5Cy8ugeCIRksEIVyCabkuLVXbMZYj1lpXgL22Fok8nv52clGfEMXA=="
+	newCID           = "zdpuAyWCG3GWfebFME3e4oG926tzpJodw4WTa9VjBwqPNiVWF"
+)
+
+func TestSchemaRoundTrip(t *testing.T) {
+	t.Parallel()
+
+	privKey := privKey(t, issuerPrivKeyCfg)
+
+	t.Run("via buffers", func(t *testing.T) {
+		t.Parallel()
+
+		// format:    dagJson   -->   PayloadModel   -->   dagCbor   -->   PayloadModel   -->   dagJson
+		// function:      DecodeDagJson()           Seal()        Unseal()          EncodeDagJson()
+
+		p1, err := attestation.FromDagJson(newDagJson)
+		require.NoError(t, err)
+
+		cborBytes, id, err := p1.ToSealed(privKey)
+		require.NoError(t, err)
+		assert.Equal(t, newCID, envelope.CIDToBase58BTC(id))
+
+		p2, c2, err := attestation.FromSealed(cborBytes)
+		require.NoError(t, err)
+		assert.Equal(t, id, c2)
+
+		readJson, err := p2.ToDagJson(privKey)
+		require.NoError(t, err)
+
+		assert.JSONEq(t, string(newDagJson), string(readJson))
+	})
+
+	t.Run("via streaming", func(t *testing.T) {
+		t.Parallel()
+
+		buf := bytes.NewBuffer(newDagJson)
+
+		// format:    dagJson   -->   PayloadModel   -->   dagCbor   -->   PayloadModel   -->   dagJson
+		// function:      DecodeDagJson()           Seal()         Unseal()         EncodeDagJson()
+
+		p1, err := attestation.FromDagJsonReader(buf)
+		require.NoError(t, err)
+
+		cborBytes := &bytes.Buffer{}
+		id, err := p1.ToSealedWriter(cborBytes, privKey)
+		require.NoError(t, err)
+		assert.Equal(t, newCID, envelope.CIDToBase58BTC(id))
+
+		p2, c2, err := attestation.FromSealedReader(cborBytes)
+		require.NoError(t, err)
+		assert.Equal(t, envelope.CIDToBase58BTC(id), envelope.CIDToBase58BTC(c2))
+
+		readJson := &bytes.Buffer{}
+		require.NoError(t, p2.ToDagJsonWriter(readJson, privKey))
+
+		assert.JSONEq(t, string(newDagJson), readJson.String())
+	})
+}
+
+func privKey(t require.TestingT, privKeyCfg string) crypto.PrivateKeySigningBytes {
+	privBytes, err := base64.StdEncoding.DecodeString(privKeyCfg)
+	require.NoError(t, err)
+
+	privKey, err := ed25519.PrivateKeyFromBytes(privBytes)
+	require.NoError(t, err)
+
+	return privKey
+}

token/attestation/testdata/new.dagjson

@@ -0,0 +1 @@
+[{"/":{"bytes":"9lfCwLn+HqFGPNMbD9mIuMjhZarhZk1mOSq2eGLIBfRM6B5dtIftDh25TOG3qJrWRvZtvupd0az/PiVv/8zMCg"}},{"h":{"/":{"bytes":"NAHtAe0BE3E"}},"ucan/att@tbd":{"claims":{"claim1":"UCAN is great"},"exp":1767790946,"iss":"did:key:z6MkmEJhVC9xHMREKTw1HpPrwVh6fcUbJ8hoVEa3UQdP9sNs","meta":{"env":"development"},"nonce":{"/":{"bytes":"jPnfQhL20Eoq/8fu"}}}}]

token/delegation/delegation.go

@@ -0,0 +1,285 @@
+// Package delegation implements the UCAN [delegation] specification with
+// an immutable Token type as well as methods to convert the Token to and
+// from the [envelope]-enclosed, signed and DAG-CBOR-encoded form that
+// should most commonly be used for transport and storage.
+//
+// [delegation]: https://github.com/ucan-wg/delegation/tree/v1_ipld
+// [envelope]: https://github.com/ucan-wg/spec#envelope
+package delegation
+
+// TODO: change the "delegation" link above when the specification is merged
+
+import (
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/MetaMask/go-did-it"
+
+	"github.com/ucan-wg/go-ucan/pkg/command"
+	"github.com/ucan-wg/go-ucan/pkg/meta"
+	"github.com/ucan-wg/go-ucan/pkg/policy"
+	"github.com/ucan-wg/go-ucan/token/internal/nonce"
+	"github.com/ucan-wg/go-ucan/token/internal/parse"
+)
+
+// Token is an immutable type that holds the fields of a UCAN delegation.
+type Token struct {
+	// Issuer DID (sender)
+	issuer did.DID
+	// Audience DID (receiver)
+	audience did.DID
+	// Principal that the chain is about (the Subject)
+	subject did.DID
+	// The Command to eventually invoke
+	command command.Command
+	// The delegation policy
+	policy policy.Policy
+	// A unique, random nonce
+	nonce []byte
+	// Arbitrary Metadata
+	meta *meta.Meta
+	// "Not before" UTC Unix Timestamp in seconds (valid from), 53-bits integer
+	notBefore *time.Time
+	// The timestamp at which the Invocation becomes invalid
+	expiration *time.Time
+}
+
+// New creates a validated delegation Token from the provided parameters and options.
+// This is typically used to delegate a given power to another agent.
+//
+// You can read it as "(issuer) allows (audience) to perform (cmd+pol) on (subject)".
+func New(iss did.DID, aud did.DID, cmd command.Command, pol policy.Policy, sub did.DID, opts ...Option) (*Token, error) {
+	tkn := &Token{
+		issuer:   iss,
+		audience: aud,
+		subject:  sub,
+		command:  cmd,
+		policy:   pol,
+		meta:     meta.NewMeta(),
+		nonce:    nil,
+	}
+
+	for _, opt := range opts {
+		if err := opt(tkn); err != nil {
+			return nil, err
+		}
+	}
+
+	var err error
+	if len(tkn.nonce) == 0 {
+		tkn.nonce, err = nonce.Generate()
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if err := tkn.validate(); err != nil {
+		return nil, err
+	}
+
+	return tkn, nil
+}
+
+// Root creates a validated UCAN delegation Token from the provided parameters and options.
+// This is typically used to create and give power to an agent.
+//
+// You can read it as "(issuer) allows (audience) to perform (cmd+pol) on itself".
+func Root(iss did.DID, aud did.DID, cmd command.Command, pol policy.Policy, opts ...Option) (*Token, error) {
+	return New(iss, aud, cmd, pol, iss, opts...)
+}
+
+// Powerline creates a validated UCAN delegation Token from the provided parameters and options.
+//
+// Powerline is a pattern for automatically delegating all future delegations to another agent regardless of Subject.
+// This is a very powerful pattern, use it only if you understand it.
+// Powerline delegations MUST NOT be used as the root delegation to a resource
+//
+// A very common use case for Powerline is providing a stable DID across multiple agents (e.g. representing a user with
+// multiple devices). This enables the automatic sharing of authority across their devices without needing to share keys
+// or set up a threshold scheme. It is also flexible, since a Powerline delegation MAY be revoked.
+//
+// You can read it as "(issuer) allows (audience) to perform (cmd+pol) on anything".
+func Powerline(iss did.DID, aud did.DID, cmd command.Command, pol policy.Policy, opts ...Option) (*Token, error) {
+	return New(iss, aud, cmd, pol, nil, opts...)
+}
+
+// Issuer returns the did.DID representing the Token's issuer.
+func (t *Token) Issuer() did.DID {
+	return t.issuer
+}
+
+// Audience returns the did.DID representing the Token's audience.
+func (t *Token) Audience() did.DID {
+	return t.audience
+}
+
+// Subject returns the did.DID representing the Token's subject.
+//
+// This field may be did.Undef for delegations that are [Powerlined] but
+// must be equal to the value returned by the Issuer method for root
+// tokens.
+func (t *Token) Subject() did.DID {
+	return t.subject
+}
+
+// Command returns the capability's command.Command.
+func (t *Token) Command() command.Command {
+	return t.command
+}
+
+// Policy returns the capability's policy.Policy.
+func (t *Token) Policy() policy.Policy {
+	return t.policy
+}
+
+// Nonce returns the random Nonce encapsulated in this Token.
+func (t *Token) Nonce() []byte {
+	return t.nonce
+}
+
+// Meta returns the Token's metadata.
+func (t *Token) Meta() meta.ReadOnly {
+	return t.meta.ReadOnly()
+}
+
+// NotBefore returns the time at which the Token becomes "active".
+func (t *Token) NotBefore() *time.Time {
+	return t.notBefore
+}
+
+// Expiration returns the time at which the Token expires.
+func (t *Token) Expiration() *time.Time {
+	return t.expiration
+}
+
+// IsRoot tells if the token is a root delegation.
+func (t *Token) IsRoot() bool {
+	return t.issuer.Equal(t.subject)
+}
+
+// IsPowerline tells if the token is a powerline delegation.
+func (t *Token) IsPowerline() bool {
+	return t.subject == nil
+}
+
+// IsValidNow verifies that the token can be used at the current time, based on expiration or "not before" fields.
+// This does NOT do any other kind of verifications.
+func (t *Token) IsValidNow() bool {
+	return t.IsValidAt(time.Now())
+}
+
+// IsValidNow verifies that the token can be used at the given time, based on expiration or "not before" fields.
+// This does NOT do any other kind of verifications.
+func (t *Token) IsValidAt(ti time.Time) bool {
+	if t.expiration != nil && ti.After(*t.expiration) {
+		return false
+	}
+	if t.notBefore != nil && ti.Before(*t.notBefore) {
+		return false
+	}
+	return true
+}
+
+func (t *Token) String() string {
+	var res strings.Builder
+
+	var kind string
+	switch {
+	case t.issuer == t.subject:
+		kind = " (root delegation)"
+	case t.subject == nil:
+		kind = " (powerline delegation)"
+	default:
+		kind = " (normal delegation)"
+	}
+
+	res.WriteString(fmt.Sprintf("Issuer: %s\n", t.Issuer()))
+	res.WriteString(fmt.Sprintf("Audience: %s\n", t.Audience()))
+	res.WriteString(fmt.Sprintf("Subject: %s%s\n", t.Subject(), kind))
+	res.WriteString(fmt.Sprintf("Command: %s\n", t.Command()))
+	res.WriteString(fmt.Sprintf("Policy: %s\n", t.Policy()))
+	res.WriteString(fmt.Sprintf("Nonce: %s\n", base64.StdEncoding.EncodeToString(t.Nonce())))
+	res.WriteString(fmt.Sprintf("Meta: %s\n", t.Meta()))
+	res.WriteString(fmt.Sprintf("NotBefore: %v\n", t.NotBefore()))
+	res.WriteString(fmt.Sprintf("Expiration: %v", t.Expiration()))
+
+	return res.String()
+}
+
+func (t *Token) validate() error {
+	var errs error
+
+	requiredDID := func(id did.DID, fieldname string) {
+		if id == nil {
+			errs = errors.Join(errs, fmt.Errorf(`a valid did is required for %s: %s`, fieldname, id.String()))
+		}
+	}
+
+	requiredDID(t.issuer, "Issuer")
+	requiredDID(t.audience, "Audience")
+
+	if len(t.nonce) < 12 {
+		errs = errors.Join(errs, fmt.Errorf("token nonce too small"))
+	}
+
+	return errs
+}
+
+// tokenFromModel build a decoded view of the raw IPLD data.
+// This function also serves as validation.
+func tokenFromModel(m tokenPayloadModel) (*Token, error) {
+	var (
+		tkn Token
+		err error
+	)
+
+	tkn.issuer, err = did.Parse(m.Iss)
+	if err != nil {
+		return nil, fmt.Errorf("parse iss: %w", err)
+	}
+
+	if tkn.audience, err = did.Parse(m.Aud); err != nil {
+		return nil, fmt.Errorf("parse audience: %w", err)
+	}
+
+	if tkn.subject, err = parse.OptionalDID(m.Sub); err != nil {
+		return nil, fmt.Errorf("parse subject: %w", err)
+	}
+
+	if tkn.command, err = command.Parse(m.Cmd); err != nil {
+		return nil, fmt.Errorf("parse command: %w", err)
+	}
+
+	if tkn.policy, err = policy.FromIPLD(m.Pol); err != nil {
+		return nil, fmt.Errorf("parse policy: %w", err)
+	}
+
+	if len(m.Nonce) == 0 {
+		return nil, fmt.Errorf("nonce is required")
+	}
+	tkn.nonce = m.Nonce
+
+	tkn.meta = m.Meta
+	if tkn.meta == nil {
+		tkn.meta = meta.NewMeta()
+	}
+
+	tkn.notBefore, err = parse.OptionalTimestamp(m.Nbf)
+	if err != nil {
+		return nil, fmt.Errorf("parse notBefore: %w", err)
+	}
+
+	tkn.expiration, err = parse.OptionalTimestamp(m.Exp)
+	if err != nil {
+		return nil, fmt.Errorf("parse expiration: %w", err)
+	}
+
+	if err := tkn.validate(); err != nil {
+		return nil, err
+	}
+
+	return &tkn, nil
+}

token/delegation/delegation.ipldsch

@@ -20,7 +20,7 @@ type Payload struct {
     nonce Bytes
 
     # Arbitrary Metadata
-    meta {String : Any}
+    meta optional {String : Any}
 
     # "Not before" UTC Unix Timestamp in seconds (valid from), 53-bits integer
     nbf optional Int

token/delegation/delegation_test.go

@@ -0,0 +1,213 @@
+package delegation_test
+
+import (
+	_ "embed"
+	"encoding/base64"
+	"testing"
+	"time"
+
+	"github.com/MetaMask/go-did-it/didtest"
+	"github.com/stretchr/testify/require"
+
+	"github.com/ucan-wg/go-ucan/pkg/command"
+	"github.com/ucan-wg/go-ucan/pkg/policy"
+	"github.com/ucan-wg/go-ucan/token/delegation"
+)
+
+//go:embed testdata/new.dagjson
+var newDagJson []byte
+
+//go:embed testdata/powerline.dagjson
+var powerlineDagJson []byte
+
+//go:embed testdata/root.dagjson
+var rootDagJson []byte
+
+const (
+	nonce = "6roDhGi0kiNriQAz7J3d+bOeoI/tj8ENikmQNbtjnD0"
+
+	subJectCmd = "/foo/bar"
+	subjectPol = `
+[
+  ["==", ".status", "draft"],
+  ["all", ".reviewer",
+    ["like", ".email", "*@example.com"]
+  ],
+  ["any", ".tags",
+    ["or", [
+      ["==", ".", "news"],
+      ["==", ".", "press"]
+    ]]
+  ]
+]
+`
+
+	aesKey = "xQklMmNTnVrmaPBq/0pwV5fEwuv/iClF5HWak9MsgI8="
+)
+
+func TestConstructors(t *testing.T) {
+	t.Parallel()
+
+	cmd, err := command.Parse(subJectCmd)
+	require.NoError(t, err)
+
+	pol, err := policy.FromDagJson(subjectPol)
+	require.NoError(t, err)
+
+	exp, err := time.Parse(time.RFC3339, "2200-01-01T00:00:00Z")
+	require.NoError(t, err)
+
+	t.Run("New", func(t *testing.T) {
+		tkn, err := delegation.New(didtest.PersonaAlice.DID(), didtest.PersonaBob.DID(), cmd, pol, didtest.PersonaCarol.DID(),
+			delegation.WithNonce([]byte(nonce)),
+			delegation.WithExpiration(exp),
+			delegation.WithMeta("foo", "fooo"),
+			delegation.WithMeta("bar", "barr"),
+		)
+		require.NoError(t, err)
+
+		require.False(t, tkn.IsRoot())
+		require.False(t, tkn.IsPowerline())
+
+		data, err := tkn.ToDagJson(didtest.PersonaAlice.PrivKey())
+		require.NoError(t, err)
+
+		require.Equal(t, newDagJson, data)
+	})
+
+	t.Run("Root", func(t *testing.T) {
+		tkn, err := delegation.Root(didtest.PersonaAlice.DID(), didtest.PersonaBob.DID(), cmd, pol,
+			delegation.WithNonce([]byte(nonce)),
+			delegation.WithExpiration(exp),
+			delegation.WithMeta("foo", "fooo"),
+			delegation.WithMeta("bar", "barr"),
+		)
+		require.NoError(t, err)
+
+		require.True(t, tkn.IsRoot())
+		require.False(t, tkn.IsPowerline())
+
+		data, err := tkn.ToDagJson(didtest.PersonaAlice.PrivKey())
+		require.NoError(t, err)
+
+		require.Equal(t, rootDagJson, data)
+	})
+
+	t.Run("Powerline", func(t *testing.T) {
+		tkn, err := delegation.Powerline(didtest.PersonaAlice.DID(), didtest.PersonaBob.DID(), cmd, pol,
+			delegation.WithNonce([]byte(nonce)),
+			delegation.WithExpiration(exp),
+			delegation.WithMeta("foo", "fooo"),
+			delegation.WithMeta("bar", "barr"),
+		)
+		require.NoError(t, err)
+
+		require.False(t, tkn.IsRoot())
+		require.True(t, tkn.IsPowerline())
+
+		data, err := tkn.ToDagJson(didtest.PersonaAlice.PrivKey())
+		require.NoError(t, err)
+
+		require.Equal(t, powerlineDagJson, data)
+	})
+}
+
+func TestEncryptedMeta(t *testing.T) {
+	t.Parallel()
+
+	cmd, err := command.Parse(subJectCmd)
+	require.NoError(t, err)
+	pol, err := policy.FromDagJson(subjectPol)
+	require.NoError(t, err)
+
+	encryptionKey, err := base64.StdEncoding.DecodeString(aesKey)
+	require.NoError(t, err)
+	require.Len(t, encryptionKey, 32)
+
+	tests := []struct {
+		name        string
+		key         string
+		value       string
+		expectError bool
+	}{
+		{
+			name:  "simple string",
+			key:   "secret1",
+			value: "hello world",
+		},
+		{
+			name:  "empty string",
+			key:   "secret2",
+			value: "",
+		},
+		{
+			name:  "special characters",
+			key:   "secret3",
+			value: "!@#$%^&*()_+-=[]{}|;:,.<>?",
+		},
+		{
+			name:  "unicode characters",
+			key:   "secret4",
+			value: "Hello, 世界! 👋",
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			tkn, err := delegation.Root(didtest.PersonaAlice.DID(), didtest.PersonaBob.DID(), cmd, pol,
+				delegation.WithEncryptedMetaString(tt.key, tt.value, encryptionKey),
+			)
+			require.NoError(t, err)
+
+			data, err := tkn.ToDagCbor(didtest.PersonaAlice.PrivKey())
+			require.NoError(t, err)
+
+			decodedTkn, _, err := delegation.FromSealed(data)
+			require.NoError(t, err)
+
+			_, err = decodedTkn.Meta().GetString(tt.key)
+			require.Error(t, err)
+
+			decrypted, err := decodedTkn.Meta().GetEncryptedString(tt.key, encryptionKey)
+			require.NoError(t, err)
+			// Verify the decrypted value is equal to the original
+			require.Equal(t, tt.value, decrypted)
+
+			// Try to decrypt with wrong key
+			wrongKey := make([]byte, 32)
+			_, err = decodedTkn.Meta().GetEncryptedString(tt.key, wrongKey)
+			require.Error(t, err)
+		})
+	}
+
+	t.Run("multiple encrypted values in the same token", func(t *testing.T) {
+		values := map[string]string{
+			"secret1": "value1",
+			"secret2": "value2",
+			"secret3": "value3",
+		}
+		var opts []delegation.Option
+		for k, v := range values {
+			opts = append(opts, delegation.WithEncryptedMetaString(k, v, encryptionKey))
+		}
+
+		// Create token with multiple encrypted values
+		tkn, err := delegation.Root(didtest.PersonaAlice.DID(), didtest.PersonaBob.DID(), cmd, pol, opts...)
+		require.NoError(t, err)
+
+		data, err := tkn.ToDagCbor(didtest.PersonaAlice.PrivKey())
+		require.NoError(t, err)
+
+		decodedTkn, _, err := delegation.FromSealed(data)
+		require.NoError(t, err)
+
+		for k, v := range values {
+			decrypted, err := decodedTkn.Meta().GetEncryptedString(k, encryptionKey)
+			require.NoError(t, err)
+			require.Equal(t, v, decrypted)
+		}
+	})
+}

token/delegation/delegationtest/README.md

@@ -0,0 +1,5 @@
+# delegationtest
+
+See the package documentation for instructions on how to use the generated
+tokens as well as information on how to regenerate the code if changes have
+been made.