diff --git a/_rsrch/cidiface/README.md b/_rsrch/cidiface/README.md
new file mode 100644
index 0000000..24dd9b7
--- /dev/null
+++ b/_rsrch/cidiface/README.md
@@ -0,0 +1,144 @@
+What golang Kinds work best to implement CIDs?
+==============================================
+
+There are many possible ways to implement CIDs.  This package explores them.
+
+### criteria
+
+There's a couple different criteria to consider:
+
+- We want the best performance when operating on the type (getters, mostly);
+- We want to minimize the number of memory allocations we need;
+- We want types which can be used as map keys, because this is common.
+
+The priority of these criteria is open to argument, but it's probably
+mapkeys > minalloc > anythingelse.
+(Mapkeys and minalloc are also quite entangled, since if we don't pick a
+representation that can work natively as a map key, we'll end up needing
+a `KeyRepr()` method which gives us something that does work as a map key,
+an that will almost certainly involve a malloc itself.)
+
+### options
+
+There are quite a few different ways to go:
+
+- Option A: CIDs as a struct; multihash as bytes.
+- Option B: CIDs as a string.
+- Option C: CIDs as an interface with multiple implementors.
+- Option D: CIDs as a struct; multihash also as a struct or string.
+- Option E: CIDs as a struct; content as strings plus offsets.
+
+The current approach on the master branch is Option A.
+
+Option D is distinctive from Option A because multihash as bytes transitively
+causes the CID struct to be non-comparible and thus not suitable for map keys
+as per https://golang.org/ref/spec#KeyType .  (It's also a bit more work to
+pursue Option D because it's just a bigger splash radius of change; but also,
+something we might also want to do soon, because we *do* also have these same
+map-key-usability concerns with multihash alone.)
+
+Option E is distinctive from Option D because Option E would always maintain
+the binary format of the cid internally, and so could yield it again without
+malloc, while still potentially having faster access to components than
+Option B since it wouldn't need to re-parse varints to access later fields.
+
+Option C is the avoid-choices choice, but note that interfaces are not free;
+since "minimize mallocs" is one of our major goals, we cannot use interfaces
+whimsically.
+
+Note there is no proposal for migrating to `type Cid []bytes`, because that
+is generally considered to be strictly inferior to `type Cid string`.
+
+
+Discoveries
+-----------
+
+### using interfaces as map keys forgoes a lot of safety checks
+
+Using interfaces as map keys pushes a bunch of type checking to runtime.
+E.g., it's totally valid at compile time to push a type which is non-comparable
+into a map key; it will panic at *runtime* instead of failing at compile-time.
+
+There's also no way to define equality checks between implementors of the
+interface: golang will always use its innate concept of comparison for the
+concrete types.  This means its effectively *never safe* to use two different
+concrete implementations of an interface in the same map; you may add elements
+which are semantically "equal" in your mind, and end up very confused later
+when both impls of the same "equal" object have been stored.
+
+### sentinel values are possible in any impl, but some are clearer than others
+
+When using `*Cid`, the nil value is a clear sentinel for 'invalid';
+when using `type Cid string`, the zero value is a clear sentinel;
+when using `type Cid struct` per Option A or D... the only valid check is
+for a nil multihash field, since version=0 and codec=0 are both valid values.
+
+### usability as a map key is important
+
+We already covered this in the criteria section, but for clarity:
+
+- Option A: ❌
+- Option B: ✔
+- Option C: ~ (caveats, and depends on concrete impl)
+- Option D: ✔
+- Option E: ✔
+
+### living without offsets requires parsing
+
+Since CID (and multihash!) are defined using varints, they require parsing;
+we can't just jump into the string at a known offset in order to yield e.g.
+the multicodec number.
+
+In order to get to the 'meat' of the CID (the multihash content), we first
+must parse:
+
+- the CID version varint;
+- the multicodec varint;
+- the multihash type enum varint;
+- and the multihash length varint.
+
+Since there are many applications where we want to jump straight to the
+multihash content (for example, when doing CAS sharding -- see the
+[disclaimer](https://github.com/multiformats/multihash#disclaimers) about
+bias in leading bytes), this overhead may be interesting.
+
+How much this overhead is significant is hard to say from microbenchmarking;
+it depends largely on usage patterns. If these traversals are a significant
+timesink, it would be an argument for Option D/E.
+If these traversals are *not* a significant timesink, we might be wiser
+to keep to Option B, because keeping a struct full of offsets will add several
+words of memory usage per CID, and we keep a *lot* of CIDs.
+
+### interfaces cause boxing which is a significant performance cost
+
+See `BenchmarkCidMap_CidStr` and friends.
+
+Long story short: using interfaces *anywhere* will cause the compiler to
+implicitly generate boxing and unboxing code (e.g. `runtime.convT2E`);
+this is both another function call, and more concerningly, results in
+large numbers of unbatchable memory allocations.
+
+Numbers without context are dangerous, but if you need one: 33%.
+It's a big deal.
+
+This means attempts to "use interfaces, but switch to concrete impls when
+performance is important" are a red herring: it doesn't work that way.
+
+This is not a general inditement against using interfaces -- but
+if a situation is at the scale where it's become important to mind whether
+or not pointers are a performance impact, then that situation also
+is one where you have to think twice before using interfaces.
+
+### one way or another: let's get rid of that star
+
+We should switch completely to handling `Cid` and remove `*Cid` completely.
+Regardless of whether we do this by migrating to interface, or string
+implementations, or simply structs with no pointers... once we get there,
+refactoring to any of the *others* can become a no-op from the perspective
+of any downstream code that uses CIDs.
+
+(This means all access via functions, never references to fields -- even if
+we were to use a struct implementation.  *Pretend* there's a interface,
+in other words.)
+
+There are probably `gofix` incantations which can help us with this migration.
diff --git a/_rsrch/cidiface/cid.go b/_rsrch/cidiface/cid.go
new file mode 100644
index 0000000..cb4b871
--- /dev/null
+++ b/_rsrch/cidiface/cid.go
@@ -0,0 +1,48 @@
+package cid
+
+import (
+	mh "github.com/multiformats/go-multihash"
+)
+
+// Cid represents a self-describing content adressed identifier.
+//
+// A CID is composed of:
+//
+//   - a Version of the CID itself,
+//   - a Multicodec (indicates the encoding of the referenced content),
+//   - and a Multihash (which identifies the referenced content).
+//
+// (Note that the Multihash further contains its own version and hash type
+// indicators.)
+type Cid interface {
+	// n.b. 'yields' means "without copy", 'produces' means a malloc.
+
+	Version() uint64         // Yields the version prefix as a uint.
+	Multicodec() uint64      // Yields the multicodec as a uint.
+	Multihash() mh.Multihash // Yields the multihash segment.
+
+	String() string // Produces the CID formatted as b58 string.
+	Bytes() []byte  // Produces the CID formatted as raw binary.
+
+	Prefix() Prefix // Produces a tuple of non-content metadata.
+
+	// some change notes:
+	// - `KeyString() CidString` is gone because we're natively a map key now, you're welcome.
+	// - `StringOfBase(mbase.Encoding) (string, error)` is skipped, maybe it can come back but maybe it should be a formatter's job.
+	// - `Equals(o Cid) bool` is gone because it's now `==`, you're welcome.
+
+	// TODO: make a multi-return method for {v,mc,mh} decomposition.  CidStr will be able to implement this more efficiently than if one makes a series of the individual getter calls.
+}
+
+// Prefix represents all the metadata of a Cid,
+// that is, the Version, the Codec, the Multihash type
+// and the Multihash length. It does not contains
+// any actual content information.
+// NOTE: The use -1 in MhLength to mean default length is deprecated,
+//   use the V0Builder or V1Builder structures instead
+type Prefix struct {
+	Version  uint64
+	Codec    uint64
+	MhType   uint64
+	MhLength int
+}
diff --git a/_rsrch/cidiface/cidBoxingBench_test.go b/_rsrch/cidiface/cidBoxingBench_test.go
new file mode 100644
index 0000000..920ce1f
--- /dev/null
+++ b/_rsrch/cidiface/cidBoxingBench_test.go
@@ -0,0 +1,71 @@
+package cid
+
+import (
+	"testing"
+)
+
+// BenchmarkCidMap_CidStr estimates how fast it is to insert primitives into a map
+// keyed by CidStr (concretely).
+//
+// We do 100 insertions per benchmark run to make sure the map initialization
+// doesn't dominate the results.
+//
+// Sample results on linux amd64 go1.11beta:
+//
+//   BenchmarkCidMap_CidStr-8          100000             16317 ns/op
+//   BenchmarkCidMap_CidIface-8        100000             20516 ns/op
+//
+// With benchmem on:
+//
+//   BenchmarkCidMap_CidStr-8          100000             15579 ns/op           11223 B/op        207 allocs/op
+//   BenchmarkCidMap_CidIface-8        100000             19500 ns/op           12824 B/op        307 allocs/op
+//   BenchmarkCidMap_StrPlusHax-8      200000             10451 ns/op            7589 B/op        202 allocs/op
+//
+// We can see here that the impact of interface boxing is significant:
+// it increases the time taken to do the inserts to 133%, largely because
+// the implied `runtime.convT2E` calls cause another malloc each.
+//
+// There are also significant allocations in both cases because
+// A) we cannot create a multihash without allocations since they are []byte;
+// B) the map has to be grown several times;
+// C) something I haven't quite put my finger on yet.
+// Ideally we'd drive those down further as well.
+//
+// Pre-allocating the map reduces allocs by a very small percentage by *count*,
+// but reduces the time taken by 66% overall (presumably because when a map
+// re-arranges itself, it involves more or less an O(n) copy of the content
+// in addition to the alloc itself).  This isn't topical to the question of
+// whether or not interfaces are a good idea; just for contextualizing.
+//
+func BenchmarkCidMap_CidStr(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		mp := map[CidStr]int{}
+		for x := 0; x < 100; x++ {
+			mp[NewCidStr(0, uint64(x), []byte{})] = x
+		}
+	}
+}
+
+// BenchmarkCidMap_CidIface is in the family of BenchmarkCidMap_CidStr:
+// it is identical except the map key type is declared as an interface
+// (which forces all insertions to be boxed, changing performance).
+func BenchmarkCidMap_CidIface(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		mp := map[Cid]int{}
+		for x := 0; x < 100; x++ {
+			mp[NewCidStr(0, uint64(x), []byte{})] = x
+		}
+	}
+}
+
+// BenchmarkCidMap_CidStrAvoidMapGrowth is in the family of BenchmarkCidMap_CidStr:
+// it is identical except the map is created with a size hint that removes
+// some allocations (5, in practice, apparently).
+func BenchmarkCidMap_CidStrAvoidMapGrowth(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		mp := make(map[CidStr]int, 100)
+		for x := 0; x < 100; x++ {
+			mp[NewCidStr(0, uint64(x), []byte{})] = x
+		}
+	}
+}
diff --git a/_rsrch/cidiface/cidString.go b/_rsrch/cidiface/cidString.go
new file mode 100644
index 0000000..129fafd
--- /dev/null
+++ b/_rsrch/cidiface/cidString.go
@@ -0,0 +1,161 @@
+package cid
+
+import (
+	"encoding/binary"
+	"fmt"
+
+	mbase "github.com/multiformats/go-multibase"
+	mh "github.com/multiformats/go-multihash"
+)
+
+//=================
+// def & accessors
+//=================
+
+var _ Cid = CidStr("")
+var _ map[CidStr]struct{} = nil
+
+// CidStr is a representation of a Cid as a string type containing binary.
+//
+// Using golang's string type is preferable over byte slices even for binary
+// data because golang strings are immutable, usable as map keys,
+// trivially comparable with built-in equals operators, etc.
+//
+// Please do not cast strings or bytes into the CidStr type directly;
+// use a parse method which validates the data and yields a CidStr.
+type CidStr string
+
+// EmptyCidStr is a constant for a zero/uninitialized/sentinelvalue cid;
+// it is declared mainly for readability in checks for sentinel values.
+const EmptyCidStr = CidStr("")
+
+func (c CidStr) Version() uint64 {
+	bytes := []byte(c)
+	v, _ := binary.Uvarint(bytes)
+	return v
+}
+
+func (c CidStr) Multicodec() uint64 {
+	bytes := []byte(c)
+	_, n := binary.Uvarint(bytes) // skip version length
+	codec, _ := binary.Uvarint(bytes[n:])
+	return codec
+}
+
+func (c CidStr) Multihash() mh.Multihash {
+	bytes := []byte(c)
+	_, n1 := binary.Uvarint(bytes)      // skip version length
+	_, n2 := binary.Uvarint(bytes[n1:]) // skip codec length
+	return mh.Multihash(bytes[n1+n2:])  // return slice of remainder
+}
+
+// String returns the default string representation of a Cid.
+// Currently, Base58 is used as the encoding for the multibase string.
+func (c CidStr) String() string {
+	switch c.Version() {
+	case 0:
+		return c.Multihash().B58String()
+	case 1:
+		mbstr, err := mbase.Encode(mbase.Base58BTC, []byte(c))
+		if err != nil {
+			panic("should not error with hardcoded mbase: " + err.Error())
+		}
+		return mbstr
+	default:
+		panic("not possible to reach this point")
+	}
+}
+
+// Bytes produces a raw binary format of the CID.
+//
+// (For CidStr, this method is only distinct from casting because of
+// compatibility with v0 CIDs.)
+func (c CidStr) Bytes() []byte {
+	switch c.Version() {
+	case 0:
+		return c.Multihash()
+	case 1:
+		return []byte(c)
+	default:
+		panic("not possible to reach this point")
+	}
+}
+
+// Prefix builds and returns a Prefix out of a Cid.
+func (c CidStr) Prefix() Prefix {
+	dec, _ := mh.Decode(c.Multihash()) // assuming we got a valid multiaddr, this will not error
+	return Prefix{
+		MhType:   dec.Code,
+		MhLength: dec.Length,
+		Version:  c.Version(),
+		Codec:    c.Multicodec(),
+	}
+}
+
+//==================================
+// parsers & validators & factories
+//==================================
+
+func NewCidStr(version uint64, codecType uint64, mhash mh.Multihash) CidStr {
+	hashlen := len(mhash)
+	// two 8 bytes (max) numbers plus hash
+	buf := make([]byte, 2*binary.MaxVarintLen64+hashlen)
+	n := binary.PutUvarint(buf, version)
+	n += binary.PutUvarint(buf[n:], codecType)
+	cn := copy(buf[n:], mhash)
+	if cn != hashlen {
+		panic("copy hash length is inconsistent")
+	}
+	return CidStr(buf[:n+hashlen])
+}
+
+// CidStrParse takes a binary byte slice, parses it, and returns either
+// a valid CidStr, or the zero CidStr and an error.
+//
+// For CidV1, the data buffer is in the form:
+//
+//     <version><codec-type><multihash>
+//
+// CidV0 are also supported. In particular, data buffers starting
+// with length 34 bytes, which starts with bytes [18,32...] are considered
+// binary multihashes.
+//
+// The multicodec bytes are not parsed to verify they're a valid varint;
+// no further reification is performed.
+//
+// Multibase encoding should already have been unwrapped before parsing;
+// if you have a multibase-enveloped string, use CidStrDecode instead.
+//
+// CidStrParse is the inverse of Cid.Bytes().
+func CidStrParse(data []byte) (CidStr, error) {
+	if len(data) == 34 && data[0] == 18 && data[1] == 32 {
+		h, err := mh.Cast(data)
+		if err != nil {
+			return EmptyCidStr, err
+		}
+		return NewCidStr(0, DagProtobuf, h), nil
+	}
+
+	vers, n := binary.Uvarint(data)
+	if err := uvError(n); err != nil {
+		return EmptyCidStr, err
+	}
+
+	if vers != 0 && vers != 1 {
+		return EmptyCidStr, fmt.Errorf("invalid cid version number: %d", vers)
+	}
+
+	_, cn := binary.Uvarint(data[n:])
+	if err := uvError(cn); err != nil {
+		return EmptyCidStr, err
+	}
+
+	rest := data[n+cn:]
+	h, err := mh.Cast(rest)
+	if err != nil {
+		return EmptyCidStr, err
+	}
+
+	// REVIEW: if the data is longer than the mh.len expects, we silently ignore it?  should we?
+	return CidStr(data[0 : n+cn+len(h)]), nil
+}
diff --git a/_rsrch/cidiface/cidStruct.go b/_rsrch/cidiface/cidStruct.go
new file mode 100644
index 0000000..2fd5fa7
--- /dev/null
+++ b/_rsrch/cidiface/cidStruct.go
@@ -0,0 +1,164 @@
+package cid
+
+import (
+	"encoding/binary"
+	"fmt"
+
+	mbase "github.com/multiformats/go-multibase"
+	mh "github.com/multiformats/go-multihash"
+)
+
+//=================
+// def & accessors
+//=================
+
+var _ Cid = CidStruct{}
+
+//var _ map[CidStruct]struct{} = nil // Will not compile!  See struct def docs.
+//var _ map[Cid]struct{} = map[Cid]struct{}{CidStruct{}: struct{}{}} // Legal to compile...
+// but you'll get panics: "runtime error: hash of unhashable type cid.CidStruct"
+
+// CidStruct represents a CID in a struct format.
+//
+// This format complies with the exact same Cid interface as the CidStr
+// implementation, but completely pre-parses the Cid metadata.
+// CidStruct is a tad quicker in case of repeatedly accessed fields,
+// but requires more reshuffling to parse and to serialize.
+// CidStruct is not usable as a map key, because it contains a Multihash
+// reference, which is a slice, and thus not "comparable" as a primitive.
+//
+// Beware of zero-valued CidStruct: it is difficult to distinguish an
+// incorrectly-initialized "invalid" CidStruct from one representing a v0 cid.
+type CidStruct struct {
+	version uint64
+	codec   uint64
+	hash    mh.Multihash
+}
+
+// EmptyCidStruct is a constant for a zero/uninitialized/sentinelvalue cid;
+// it is declared mainly for readability in checks for sentinel values.
+//
+// Note: it's not actually a const; the compiler does not allow const structs.
+var EmptyCidStruct = CidStruct{}
+
+func (c CidStruct) Version() uint64 {
+	return c.version
+}
+
+func (c CidStruct) Multicodec() uint64 {
+	return c.codec
+}
+
+func (c CidStruct) Multihash() mh.Multihash {
+	return c.hash
+}
+
+// String returns the default string representation of a Cid.
+// Currently, Base58 is used as the encoding for the multibase string.
+func (c CidStruct) String() string {
+	switch c.Version() {
+	case 0:
+		return c.Multihash().B58String()
+	case 1:
+		mbstr, err := mbase.Encode(mbase.Base58BTC, c.Bytes())
+		if err != nil {
+			panic("should not error with hardcoded mbase: " + err.Error())
+		}
+		return mbstr
+	default:
+		panic("not possible to reach this point")
+	}
+}
+
+// Bytes produces a raw binary format of the CID.
+func (c CidStruct) Bytes() []byte {
+	switch c.version {
+	case 0:
+		return []byte(c.hash)
+	case 1:
+		// two 8 bytes (max) numbers plus hash
+		buf := make([]byte, 2*binary.MaxVarintLen64+len(c.hash))
+		n := binary.PutUvarint(buf, c.version)
+		n += binary.PutUvarint(buf[n:], c.codec)
+		cn := copy(buf[n:], c.hash)
+		if cn != len(c.hash) {
+			panic("copy hash length is inconsistent")
+		}
+		return buf[:n+len(c.hash)]
+	default:
+		panic("not possible to reach this point")
+	}
+}
+
+// Prefix builds and returns a Prefix out of a Cid.
+func (c CidStruct) Prefix() Prefix {
+	dec, _ := mh.Decode(c.hash) // assuming we got a valid multiaddr, this will not error
+	return Prefix{
+		MhType:   dec.Code,
+		MhLength: dec.Length,
+		Version:  c.version,
+		Codec:    c.codec,
+	}
+}
+
+//==================================
+// parsers & validators & factories
+//==================================
+
+// CidStructParse takes a binary byte slice, parses it, and returns either
+// a valid CidStruct, or the zero CidStruct and an error.
+//
+// For CidV1, the data buffer is in the form:
+//
+//     <version><codec-type><multihash>
+//
+// CidV0 are also supported. In particular, data buffers starting
+// with length 34 bytes, which starts with bytes [18,32...] are considered
+// binary multihashes.
+//
+// The multicodec bytes are not parsed to verify they're a valid varint;
+// no further reification is performed.
+//
+// Multibase encoding should already have been unwrapped before parsing;
+// if you have a multibase-enveloped string, use CidStructDecode instead.
+//
+// CidStructParse is the inverse of Cid.Bytes().
+func CidStructParse(data []byte) (CidStruct, error) {
+	if len(data) == 34 && data[0] == 18 && data[1] == 32 {
+		h, err := mh.Cast(data)
+		if err != nil {
+			return EmptyCidStruct, err
+		}
+		return CidStruct{
+			codec:   DagProtobuf,
+			version: 0,
+			hash:    h,
+		}, nil
+	}
+
+	vers, n := binary.Uvarint(data)
+	if err := uvError(n); err != nil {
+		return EmptyCidStruct, err
+	}
+
+	if vers != 0 && vers != 1 {
+		return EmptyCidStruct, fmt.Errorf("invalid cid version number: %d", vers)
+	}
+
+	codec, cn := binary.Uvarint(data[n:])
+	if err := uvError(cn); err != nil {
+		return EmptyCidStruct, err
+	}
+
+	rest := data[n+cn:]
+	h, err := mh.Cast(rest)
+	if err != nil {
+		return EmptyCidStruct, err
+	}
+
+	return CidStruct{
+		version: vers,
+		codec:   codec,
+		hash:    h,
+	}, nil
+}
diff --git a/_rsrch/cidiface/enums.go b/_rsrch/cidiface/enums.go
new file mode 100644
index 0000000..53e3d47
--- /dev/null
+++ b/_rsrch/cidiface/enums.go
@@ -0,0 +1,76 @@
+package cid
+
+// These are multicodec-packed content types. The should match
+// the codes described in the authoritative document:
+// https://github.com/multiformats/multicodec/blob/master/table.csv
+const (
+	Raw = 0x55
+
+	DagProtobuf = 0x70
+	DagCBOR     = 0x71
+
+	GitRaw = 0x78
+
+	EthBlock           = 0x90
+	EthBlockList       = 0x91
+	EthTxTrie          = 0x92
+	EthTx              = 0x93
+	EthTxReceiptTrie   = 0x94
+	EthTxReceipt       = 0x95
+	EthStateTrie       = 0x96
+	EthAccountSnapshot = 0x97
+	EthStorageTrie     = 0x98
+	BitcoinBlock       = 0xb0
+	BitcoinTx          = 0xb1
+	ZcashBlock         = 0xc0
+	ZcashTx            = 0xc1
+	DecredBlock        = 0xe0
+	DecredTx           = 0xe1
+)
+
+// Codecs maps the name of a codec to its type
+var Codecs = map[string]uint64{
+	"v0":                   DagProtobuf,
+	"raw":                  Raw,
+	"protobuf":             DagProtobuf,
+	"cbor":                 DagCBOR,
+	"git-raw":              GitRaw,
+	"eth-block":            EthBlock,
+	"eth-block-list":       EthBlockList,
+	"eth-tx-trie":          EthTxTrie,
+	"eth-tx":               EthTx,
+	"eth-tx-receipt-trie":  EthTxReceiptTrie,
+	"eth-tx-receipt":       EthTxReceipt,
+	"eth-state-trie":       EthStateTrie,
+	"eth-account-snapshot": EthAccountSnapshot,
+	"eth-storage-trie":     EthStorageTrie,
+	"bitcoin-block":        BitcoinBlock,
+	"bitcoin-tx":           BitcoinTx,
+	"zcash-block":          ZcashBlock,
+	"zcash-tx":             ZcashTx,
+	"decred-block":         DecredBlock,
+	"decred-tx":            DecredTx,
+}
+
+// CodecToStr maps the numeric codec to its name
+var CodecToStr = map[uint64]string{
+	Raw:                "raw",
+	DagProtobuf:        "protobuf",
+	DagCBOR:            "cbor",
+	GitRaw:             "git-raw",
+	EthBlock:           "eth-block",
+	EthBlockList:       "eth-block-list",
+	EthTxTrie:          "eth-tx-trie",
+	EthTx:              "eth-tx",
+	EthTxReceiptTrie:   "eth-tx-receipt-trie",
+	EthTxReceipt:       "eth-tx-receipt",
+	EthStateTrie:       "eth-state-trie",
+	EthAccountSnapshot: "eth-account-snapshot",
+	EthStorageTrie:     "eth-storage-trie",
+	BitcoinBlock:       "bitcoin-block",
+	BitcoinTx:          "bitcoin-tx",
+	ZcashBlock:         "zcash-block",
+	ZcashTx:            "zcash-tx",
+	DecredBlock:        "decred-block",
+	DecredTx:           "decred-tx",
+}
diff --git a/_rsrch/cidiface/errors.go b/_rsrch/cidiface/errors.go
new file mode 100644
index 0000000..588c62e
--- /dev/null
+++ b/_rsrch/cidiface/errors.go
@@ -0,0 +1,24 @@
+package cid
+
+import (
+	"errors"
+)
+
+var (
+	// ErrVarintBuffSmall means that a buffer passed to the cid parser was not
+	// long enough, or did not contain an invalid cid
+	ErrVarintBuffSmall = errors.New("reading varint: buffer too small")
+
+	// ErrVarintTooBig means that the varint in the given cid was above the
+	// limit of 2^64
+	ErrVarintTooBig = errors.New("reading varint: varint bigger than 64bits" +
+		" and not supported")
+
+	// ErrCidTooShort means that the cid passed to decode was not long
+	// enough to be a valid Cid
+	ErrCidTooShort = errors.New("cid too short")
+
+	// ErrInvalidEncoding means that selected encoding is not supported
+	// by this Cid version
+	ErrInvalidEncoding = errors.New("invalid base encoding")
+)
diff --git a/_rsrch/cidiface/misc.go b/_rsrch/cidiface/misc.go
new file mode 100644
index 0000000..9a4486a
--- /dev/null
+++ b/_rsrch/cidiface/misc.go
@@ -0,0 +1,12 @@
+package cid
+
+func uvError(read int) error {
+	switch {
+	case read == 0:
+		return ErrVarintBuffSmall
+	case read < 0:
+		return ErrVarintTooBig
+	default:
+		return nil
+	}
+}