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Registry of Uniform Resource (UR) Types

BCR-2020-006

© 2020 Blockchain Commons

Authors: Wolf McNally, Christopher Allen
Date: May 12, 2020
Revised: November 25, 2023

Introduction

A limited, base-32 character set is required by Uniform Resources (UR) [BCR5] in order to be compatible with both URI syntax [RFC3986] and QR Code alphanumeric mode [QRCodeAlphaNum]. In addition, [BCR5] specifies:

Each UR encoded object includes a type component as the first path component after the UR scheme. Types MUST consist only of characters from the English letters (ignoring case), Arabic numerals, and the hyphen -.

Because this namespace intersects with but does not enclose existing type namespace definitions such as [MIME] and because defined types like MIME do not uniformly specify CBOR encoding (required by [BCR5]) a new namespace is necessary to easily identify the type of data encoded in a UR.

This document is a registry of UR types and CBOR tags maintained by Blockchain Commons. Each entry in the registry records the type string, its associated CBOR tag, a brief description of the type, and either a link to the type definition or a reference to the type definition within this document. Additional types may be added by contacting this document's maintainers.

Types specified within this document are specified in [CDDL], the Concise Data Definition Language used as a human-readable notation for CBOR structures.

User-Defined Types x-*

All types with the prefix x- are reserved for user-defined UR types.

CBOR-Wrapped Types cbor-*

All types with the prefix cbor- are reserved for existing non-CBOR media types wrapped in a CBOR byte string. The only types currently specified in this registry are cbor-png for [PNG] images and cbor-svg for [SVG] images.

Tags for Embedding

Each UR type defines a CBOR encoding. When a UR type is suitable for embedding within another CBOR structure, it MUST be tagged with a CBOR tag defined for this purpose. When a UR type is used as the top-level CBOR object encoded into a UR, the object MUST NOT be tagged, as this information is provided by the UR type component.

This document also lists the tag, if any, defined for the particular CBOR structure contained in the UR encoding. The tags listed here may or may not currently be listed in IANA's registry of CBOR tags [CBOR-TAGS] but the intent is that they will be registered as they come into us.

Some of the UR types and their corresponding CBOR tags below have been deprecated. There may be existing software that still uses these "version 1" types and tags however, so it is RECOMMENDED that such software only read the deprecated types and tags and not write them, preferring the version 2 types and tags instead. Deprecated types and tags below are denoted using strikethrough.

Registry

UR Type CBOR Tag Description Definition
envelope 200 Gordian Envelope [Envelope]
known-value 40000 Envelope known value [BCR-2023-002]
digest 40001 Cryptographic digest [BCR-2021-002]
encrypted 40002 Encrypted message [BCR-2022-001]
compressed 40003 Compressed message [BCR-2023-001]
request 40004 GSTP request [BCR-2023-014]
response 40005 GSTP response [BCR-2023-014]
function 40006 Function identifier [BCR-2023-012]
parameter 40007 Parameter identifier [BCR-2023-012]
placeholder 40008 Function placeholder [BCR-2023-012]
replacement 40009 Function replacement [BCR-2023-012]
seed crypto-seed 40300 300 Cryptographic seed This document
agreement-private-key 40010 Agreement private key [BCR-2023-011]
agreement-public-key 40011 Agreement private key [BCR-2023-011]
hdkey crypto-hdkey 40303 303 Hierarchical Deterministic (HD) key [BCR-2020-007]
keypath crypto-keypath 40304 304 Key Derivation Path [BCR-2020-007]
coin-info crypto-coin-info 40305 305 Cryptocurrency Coin Use [BCR-2020-007]
eckey crypto-eckey 40306 306 Elliptic Curve (EC) key [BCR-2020-008]
address crypto-address 40307 307 Cryptocurrency Address [BCR-2020-009]
output-descriptor crypto-output 40308 308 Bitcoin Output Descriptor [BCR-2020-010]
sskr crypto-sskr 40309 309 SSKR (Sharded Secret Key Reconstruction) shard [BCR-2020-011]
psbt crypto-psbt 40310 310 Partially Signed Bitcoin Transaction (PSBT) This document
account-descriptor crypto-account 40311 311 BIP44 Account [BCR-2023-019]
arid 40012 Apparently Random Identifier [BCR-2022-002]
nonce 40014 Cryptographic nonce [BCR-2023-015]
password 40015 Hashed password (e.g., Scrypt) [BCR-2023-016]
crypto-prvkeys 40016 Private key base [BCR-2023-011]
crypto-pubkeys 40017 Public key base [BCR-2023-011]
salt 40018 Salt [BCR-2023-017]
crypto-sealed 40019 Sealed message [BCR-2023-011]
signature 40020 Signature [BCR-2023-011]
signing-private-key 40021 Signing private key [BCR-2023-011]
signing-public-key 40022 Signing public key [BCR-2023-011]
crypto-key 40023 Symmetric Key [BCR-2022-001]
ssh-private 40800 Text format SSH private key [BCR-2024-005]
ssh-public 40801 Text format SSH public key [BCR-2024-005]
ssh-signature 40802 Text format SSH signature [BCR-2024-005]
ssh-certificate 40803 Text format SSH certificate [BCR-2024-005]

Notable Tags

UR Type CBOR Tag Description Definition
cbor 24 Wrapped cbor [CBOR]
cbor-png PNG image [PNG]
cbor-svg SVG image [SVG]
cose-sign 98 COSE_Sign: Signed message (multiple recipients) [COSE]
cose-sign1 18 COSE_Sign1: Signed message (single recipient) [COSE]
cose-encrypt 96 COSE_Encrypt: Encrypted message (multiple recipients) [COSE]
cose-encrypt0 16 COSE_Encrypt0: Encrypted message (implied recipient) [COSE]
cose-mac 97 COSE_Mac: Authenticated message (multiple recipients) [COSE]
cose-mac0 17 COSE_Mac0: Authenticated message (implied recipient) [COSE]
cose-key COSE_Key: An encryption key [COSE]
cose-keyset COSE_KeySet: A set of encryption keys [COSE]

UR Types and CBOR Tags

This document defines the following UR types along with their corresponding CBOR tags:

UR type CBOR Tag
ur:seed #6.40300

These tags have been registered in the IANA Registry of CBOR Tags.

Cryptographic Seed seed

The type seed contains a single, byte string having a length from 1 to 64 bytes. Semantically, this byte string SHOULD be a random or pseudorandom sequence generated by a cryptographically-strong algorithm.

The type may also include a creation-date attribute which is the number of days since the Unix epoch upon which this seed was generated. See BCR-2023-008 for more information.

The type may also include name, which SHOULD be a short name for the seed, and note, which is an arbitrary amount of text describing the seed.

CDDL

tagged-seed = #6.40300(seed)

seed = {
	payload: bytes,
	? creation-date: tagged-date,
	? name: text,
	? note: text
}
payload = 1
creation-date = 2
name = 3
note = 4

Example/Test Vector

  • For a 16 byte (128-bit) seed generated on May 11, 2020, in the CBOR diagnostic notation:
{
  1: h'c7098580125e2ab0981253468b2dbc52',
  2: 100(18394)
}
  • Encoded as binary using [CBOR-PLAYGROUND]:
A2                                     # map(2)
   01                                  # unsigned(1) payload:
   50                                  # bytes(16)
      C7098580125E2AB0981253468B2DBC52 # payload
   02                                  # unsigned(2) creation-date:
   D8 64                               # tag(100)
      19 47DA                          # unsigned(18394)
  • As a hex string:
A20150C7098580125E2AB0981253468B2DBC5202D8641947DA
  • As a UR:
ur:seed/oeadgdstaslplabghydrpfmkbggufgludprfgmaotpiecffltnlpqdenos
  • UR as QR Code:

Seed Digest Source Specification

When a unique identifier to a seed is needed, an extract of its fields, called the digest source is created and then used as input to the SHA-256 hashing algorithm. The resulting digest can be compared to digests produced the same way to determine whether a seed has a particular identity. See BCR-2021-002: Digests for Digital Objects for more information.

The digest source of a seed is just the payload byte string. All other fields are ignored. For the example test vector above, the payload is:

c7098580125e2ab0981253468b2dbc52

So the digest would be the SHA-256 hash of those bytes:

e824467caffeaf3bbc3e0ca095e660a9bad80ddb6a919433a37161908b9a3986

When encoded as CBOR (diagnostic notation):

seed-digest = #6.40600(h'e824467caffeaf3bbc3e0ca095e660a9bad80ddb6a919433a37161908b9a3986')

Encoded as binary:

D9 0258                                 # tag(600)
   58 20                                # bytes(32)
      E824467CAFFEAF3BBC3E0CA095E660A9BAD80DDB6A919433A37161908B9A3986

Partially Signed Bitcoin Transaction (PSBT) psbt

The type psbt contains a single, deterministic length byte string of variable length up to 2^32-1 bytes. Semantically, this byte string MUST be a valid Partially Signed Bitcoin Transaction encoded in the binary format specified by [BIP174].

CDDL

bytes

Example/Test Vector

  • CBOR diagnostic notation:
h'70736274ff01009a020000000258e87a21b56daf0c23be8e7070456c336f7cbaa5c8757924f545887bb2abdd750000000000ffffffff838d0427d0ec650a68aa46bb0b098aea4422c071b2ca78352a077959d07cea1d0100000000ffffffff0270aaf00800000000160014d85c2b71d0060b09c9886aeb815e50991dda124d00e1f5050000000016001400aea9a2e5f0f876a588df5546e8742d1d87008f000000000000000000'
  • Encoded as binary using [CBOR-PLAYGROUND]:
58 A7                                   # bytes(167)
70736274FF01009A020000000258E87A21B56DAF0C23BE8E7070456C336F7CBAA5C8757924F545887BB2ABDD750000000000FFFFFFFF838D0427D0EC650A68AA46BB0B098AEA4422C071B2CA78352A077959D07CEA1D0100000000FFFFFFFF0270AAF00800000000160014D85C2B71D0060B09C9886AEB815E50991DDA124D00E1F5050000000016001400AEA9A2E5F0F876A588DF5546E8742D1D87008F000000000000000000
  • As a hex string:
58A770736274FF01009A020000000258E87A21B56DAF0C23BE8E7070456C336F7CBAA5C8757924F545887BB2ABDD750000000000FFFFFFFF838D0427D0EC650A68AA46BB0B098AEA4422C071B2CA78352A077959D07CEA1D0100000000FFFFFFFF0270AAF00800000000160014D85C2B71D0060B09C9886AEB815E50991DDA124D00E1F5050000000016001400AEA9A2E5F0F876A588DF5546E8742D1D87008F000000000000000000
  • As a UR:
ur:psbt/hdosjojkidjyzmadaenyaoaeaeaeaohdvsknclrejnpebncnrnmnjojofejzeojlkerdonspkpkkdkykfelokgprpyutkpaeaeaeaeaezmzmzmzmlslgaaditiwpihbkispkfgrkbdaslewdfycprtjsprsgksecdratkkhktikewdcaadaeaeaeaezmzmzmzmaojopkwtayaeaeaeaecmaebbtphhdnjstiambdassoloimwmlyhygdnlcatnbggtaevyykahaeaeaeaecmaebbaeplptoevwwtyakoonlourgofgvsjydpcaltaemyaeaeaeaeaeaeaeaeaebkgdcarh
  • UR as QR Code:

COSE Structures cose-*

[COSE] specifies CBOR-encoded structures for transmitting signed and/or encrypted objects. This document specifies UR types starting with cose- for the various COSE messages in their untagged form.

Implementations

Typescript/Javascript Implementation: ur-registry

Java Implementation: hummingbird

Normative References

Informative References