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Versions: 00

Individual Submission                                      J. Snell, Ed.
Internet-Draft                                         NearForm Research
Intended status: Standards Track                                N. Greco
Expires: August 27, 2020                                        J. Benet
                                                            D. Dalrymple
                                                                 D. Dias
                                                               L. Gierth
                                                           Protocol Labs
                                                       February 24, 2020


                              Multiformats
                        draft-snell-multihash-00

Abstract

   Defines Multiformats, a collection of data formats that aim to
   future-proof systems by adding self-description to format values; and
   defines the Multihash and Multibase Multiformat data formats.

Status of This Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on August 27, 2020.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Unsigned Variable Length Integer  . . . . . . . . . . . . . .   3
     2.1.  ABNF Definition . . . . . . . . . . . . . . . . . . . . .   4
   3.  Multibase . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Multibase ABNF  . . . . . . . . . . . . . . . . . . . . .   4
   4.  Multihash . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Example Multihashes . . . . . . . . . . . . . . . . . . .   5
     4.2.  Multihash ABNF  . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  The Codec Registry  . . . . . . . . . . . . . . . . . . .   6
       6.1.1.  Codec Registration  . . . . . . . . . . . . . . . . .   6
       6.1.2.  Initial Contents  . . . . . . . . . . . . . . . . . .   7
     6.2.  The Multibase Registry  . . . . . . . . . . . . . . . . .  15
       6.2.1.  Base-Encoding Registration  . . . . . . . . . . . . .  15
       6.2.2.  Initial Contents  . . . . . . . . . . . . . . . . . .  16
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   Multiformats are a collection of data formats that aim to future-
   proof systems by adding self-description to format values; allowing
   interoperability and protocol agility while avoiding lock in.

   The self-describing aspects of the Multiformat values have a few
   stipulations:

   o  They MUST be in-band (encoded within and carried with the value).

   o  They MUST avoid lock-in and promote extensibility.

   o  They MUST be compact and have a binary-packed representation.

   o  They MUST have a human-readable representation.

   This specification defines the Multihash and Multibase formats.

   This specification also defines extensible registries for codec and
   base-encoding identifiers.

   New Multiformat data formats SHOULD be registered within the Codec
   Registry using the "multiformat" type identifier.





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   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   and "OPTIONAL" are to be interpreted as described in [RFC2119].

   This specification uses the Augmented Backus-Naur Form (ABNF)
   notation of [RFC5234]

2.  Unsigned Variable Length Integer

   The various Multiformats defined in this specification make use of
   the Unsigned Variable Length Integer encoding defined in Appendix C
   of the [LEB128] standard.

   As suggested by the name, this variable length encoding is only
   capable of representing unsigned integers.  Further, while there is
   no theoretical maximum integer value that can be represented by the
   format, implementations MUST NOT encode more than nine (9) bytes
   giving a practical limit of integers in a range between 0 and 2^63 -
   1.

   Specific Multiformats using the Unsigned Variable Length Integer
   encoding MAY explicitly declare a more restricted range of encoded
   values but MUST NOT require values greater than 2^63 - 1.

   All integer values between 0 and 127 are encoded as a single byte
   that is identical to the input.  That is, the value 1 is encoded as
   00000001, and the value 127 is encoded as 01111111.

   Values greater than 127 require two or more bytes as illustrated in
   the examples below.

   Numbers MUST be encoded using the least number of bytes possible.

                 +---------+----------------------------+
                 | Integer | Encoding                   |
                 +---------+----------------------------+
                 | 1       | 00000001                   |
                 | 127     | 01111111                   |
                 | 128     | 10000000 00000001          |
                 | 255     | 11111111 00000001          |
                 | 300     | 10101100 00000010          |
                 | 16384   | 10000000 10000000 00000001 |
                 +---------+----------------------------+








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2.1.  ABNF Definition

   Specifications signal use of the Unsigned Variable Length Encoded
   Integer format by referencing the unsigned-varint ABNF grammar rule
   defined below.

   varint-terminator = %x00-7f
   varint-continuation = %x80-ff
   unsigned-varint = *8varint-continuation varint-terminator

3.  Multibase

   Multibase is a format for differentiating outputs from various well-
   established text base-encoding algorithms.

   A Multibase consists simply of a single prefix character that
   identifies the base-encoding of the remaining characters.  All valid
   Multibase prefix characters are registered in The Multibase Registry.

   The prefix character for each base are selected such that they are
   included in the alphabets of the base they represent.  For example,
   "f" is the base code for base16 (hex) because "f" is in hex's 16
   character alphabet.

3.1.  Examples

   Given the sample text, "Multibase is awesome! \o/", the following
   example Multibase encodings may be generated.

   +------------+-----------------------------------------------------+
   | Base       | Multibase                                           |
   +------------+-----------------------------------------------------+
   | 16 (upper) | F4D756C74696261736520697320617765736F6D6521205C6F2F |
   | 16 (lower) | f4d756c74696261736520697320617765736f6d6521205c6f2f |
   | 32         | BJV2WY5DJMJQXGZJANFZSAYLXMVZW63LFEEQFY3ZP           |
   | 58         | zYAjKoNbau5KiqmHPmSxYCvn66dA1vLmwbt                 |
   | 64         | MTXVsdGliYXNlIGlzIGF3ZXNvbWUhIFxvLw==               |
   +------------+-----------------------------------------------------+

3.2.  Multibase ABNF

   ABNF

   base-identifier = <ascii character>
   multibase = base-identifier {base-encoded-data}






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4.  Multihash

   Multihash is a format for differentiating outputs from various well-
   established cryptographic hash functions while adressing output
   length and encoding considerations.

   Multihash values encode the hash function output prefixed by an id
   identifying the hash function encoded as an unsigned variable length
   integer, and the length of the hash function output encoded as an
   unsigned variable length integer.  All valid Multihash function
   identifiers are registered in the Codec Registry.

   Multihash values are byte sequences that MAY be encoded in multiple
   base-encodings including hex, base64, base32, or others.  When
   representing a Multihash using a base-encoding, the Multibase format
   SHOULD be used.

4.1.  Example Multihashes

   Given the sample text "multihash", the following example Multihash
   values may be generated:

   +--------+-----+----------------------------------------------------+
   | Functi | ID  | Multihash (Multibase/Base16)                       |
   | on     |     |                                                    |
   +--------+-----+----------------------------------------------------+
   | sha1   | 0x1 | f111488c2f11fb2ce392acb5b2986e640211c4690073e      |
   |        | 1   |                                                    |
   | sha2-2 | 0x1 | f12209cbc07c3f991725836a3aa2a581ca2029198aa420b9d9 |
   | 56     | 2   | 9bc0e131d9f3e2cbe47                                |
   +--------+-----+----------------------------------------------------+

4.2.  Multihash ABNF

   Multihash

   hash-function-code = unsigned-varint
   hash-digest-size = unsigned-varint
   hash = {hash function output}

   multihash = hash-function-code hash-digest-size hash

5.  Security Considerations

   There are no additional security considerations introduced by the use
   of Multiformat data formats.  Note, however, that various hash
   functions that may be used with multiformats may be vulnerable to




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   various known security issues and limitations (e.g. sha1) and thus
   SHOULD be avoided.

6.  IANA Considerations

6.1.  The Codec Registry

6.1.1.  Codec Registration

   Codec identifiers can be registered using the procedure described
   herein.

   Codecs are registered using the Expert Review policy (see Section 4.5
   of [RFC8126]).  The goal of the registry is to reflect common use of
   codecs on the Internet.  Therefore, the expert(s) should be strongly
   biased towards approving registrations, unless they are abusive,
   frivolous, not likely to be used on the Internet, or actively harmful
   to the Internet and/or the Web (not merely aesthetically displeasing
   or architecturally dubious).  Expert(s) can withhold registration of
   codecs that are too general for the proposal application.

   Expert(s) will clearly identify any issues that cause a registration
   to be refused.  Advice about the semantics of a proposed codec can be
   given, but if it does not block registration, this should be
   explicitly stated.

   When a request if approved, the expert(s) shall inform IANA, and the
   regstration will be processed.  The IESG is the final arbiter of any
   objection.

   The Codec Registry is located at https://www.iana.org/assignments/
   multiformat-codecs.  Registration requests can be made by following
   instructions located there or by sending an email to the multiformat-
   codecs@ietf.org mailing list.

   Registration requests consist of at least the following information:

   o  *Codec Name*: The name of codec

   o  *Type*: The type of applicable multiformat

   o  *Code*: The requested identity code

   o  *Description*: An optional short text description of the codec.

   o  *Reference*: A reference to the document that specifies the codec,
      preferably including a URI that can be used to retrieve a copy of




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      the document.  An indication of the relevant section(s) can also
      be included but is not required.

   Multiformat data formats themselves MAY be registered within The
   Codec Registry using a Type field value of "multiformat".  For all
   other registrations, the Type field MUST refer to an entry in The
   Codec Registry whose Type is "multiformat".

   The expert(s) can define additional fields to be collected in the
   registry.

   Registrations SHOULD reference a freely available, stable
   specification.

   Note that codecs can be registere by third parties (including the
   expert(s)), if the expert(s) determine that an unregistered codec is
   widely deployed and not likely to be registered in a timely manner
   otherwise.  Such registrations still are subject to the requirements
   defined.

6.1.2.  Initial Contents

   The initial contents of the Codec Registry include:

   +----------------+-------------+--------+---------------------------+
   | Name           | Type        | Code   | Description               |
   +----------------+-------------+--------+---------------------------+
   | identity       | multihash   | 0x00   | raw binary                |
   | sha1           | multihash   | 0x11   |                           |
   | sha2-256       | multihash   | 0x12   |                           |
   | sha2-512       | multihash   | 0x13   |                           |
   | sha3-512       | multihash   | 0x14   |                           |
   | sha3-384       | multihash   | 0x15   |                           |
   | sha3-256       | multihash   | 0x16   |                           |
   | sha3-224       | multihash   | 0x17   |                           |
   | shake-128      | multihash   | 0x18   |                           |
   | shake-256      | multihash   | 0x19   |                           |
   | keccak-224     | multihash   | 0x1a   | keccak has variable       |
   |                |             |        | output length. The number |
   |                |             |        | specifies the core length |
   | keccak-256     | multihash   | 0x1b   |                           |
   | keccak-384     | multihash   | 0x1c   |                           |
   | keccak-512     | multihash   | 0x1d   |                           |
   | murmur3-128    | multihash   | 0x22   |                           |
   | murmur3-32     | multihash   | 0x23   |                           |
   | multicodec     | multiformat | 0x30   |                           |
   | multihash      | multiformat | 0x31   |                           |
   | multibase      | multiformat | 0x33   |                           |



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   | dbl-sha2-256   | multihash   | 0x56   |                           |
   | md4            | multihash   | 0xd4   |                           |
   | md5            | multihash   | 0xd5   |                           |
   | bmt            | multihash   | 0xd6   | Binary Merkle Tree Hash   |
   | x11            | multihash   | 0x1100 |                           |
   | blake2b-8      | multihash   | 0xb201 | Blake2b consists of 64    |
   |                |             |        | output lengths that give  |
   |                |             |        | different hashes          |
   | blake2b-16     | multihash   | 0xb202 |                           |
   | blake2b-24     | multihash   | 0xb203 |                           |
   | blake2b-32     | multihash   | 0xb204 |                           |
   | blake2b-40     | multihash   | 0xb205 |                           |
   | blake2b-48     | multihash   | 0xb206 |                           |
   | blake2b-56     | multihash   | 0xb207 |                           |
   | blake2b-64     | multihash   | 0xb208 |                           |
   | blake2b-72     | multihash   | 0xb209 |                           |
   | blake2b-80     | multihash   | 0xb20a |                           |
   | blake2b-88     | multihash   | 0xb20b |                           |
   | blake2b-96     | multihash   | 0xb20c |                           |
   | blake2b-104    | multihash   | 0xb20d |                           |
   | blake2b-112    | multihash   | 0xb20e |                           |
   | blake2b-120    | multihash   | 0xb20f |                           |
   | blake2b-128    | multihash   | 0xb210 |                           |
   | blake2b-136    | multihash   | 0xb211 |                           |
   | blake2b-144    | multihash   | 0xb212 |                           |
   | blake2b-152    | multihash   | 0xb213 |                           |
   | blake2b-160    | multihash   | 0xb214 |                           |
   | blake2b-168    | multihash   | 0xb215 |                           |
   | blake2b-176    | multihash   | 0xb216 |                           |
   | blake2b-184    | multihash   | 0xb217 |                           |
   | blake2b-192    | multihash   | 0xb218 |                           |
   | blake2b-200    | multihash   | 0xb219 |                           |
   | blake2b-208    | multihash   | 0xb21a |                           |
   | blake2b-216    | multihash   | 0xb21b |                           |
   | blake2b-224    | multihash   | 0xb21c |                           |
   | blake2b-232    | multihash   | 0xb21d |                           |
   | blake2b-240    | multihash   | 0xb21e |                           |
   | blake2b-248    | multihash   | 0xb21f |                           |
   | blake2b-256    | multihash   | 0xb220 |                           |
   | blake2b-264    | multihash   | 0xb221 |                           |
   | blake2b-272    | multihash   | 0xb222 |                           |
   | blake2b-280    | multihash   | 0xb223 |                           |
   | blake2b-288    | multihash   | 0xb224 |                           |
   | blake2b-296    | multihash   | 0xb225 |                           |
   | blake2b-304    | multihash   | 0xb226 |                           |
   | blake2b-312    | multihash   | 0xb227 |                           |
   | blake2b-320    | multihash   | 0xb228 |                           |
   | blake2b-328    | multihash   | 0xb229 |                           |



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   | blake2b-336    | multihash   | 0xb22a |                           |
   | blake2b-344    | multihash   | 0xb22b |                           |
   | blake2b-352    | multihash   | 0xb22c |                           |
   | blake2b-360    | multihash   | 0xb22d |                           |
   | blake2b-368    | multihash   | 0xb22e |                           |
   | blake2b-376    | multihash   | 0xb22f |                           |
   | blake2b-384    | multihash   | 0xb230 |                           |
   | blake2b-392    | multihash   | 0xb231 |                           |
   | blake2b-400    | multihash   | 0xb232 |                           |
   | blake2b-408    | multihash   | 0xb233 |                           |
   | blake2b-416    | multihash   | 0xb234 |                           |
   | blake2b-424    | multihash   | 0xb235 |                           |
   | blake2b-432    | multihash   | 0xb236 |                           |
   | blake2b-440    | multihash   | 0xb237 |                           |
   | blake2b-448    | multihash   | 0xb238 |                           |
   | blake2b-456    | multihash   | 0xb239 |                           |
   | blake2b-464    | multihash   | 0xb23a |                           |
   | blake2b-472    | multihash   | 0xb23b |                           |
   | blake2b-480    | multihash   | 0xb23c |                           |
   | blake2b-488    | multihash   | 0xb23d |                           |
   | blake2b-496    | multihash   | 0xb23e |                           |
   | blake2b-504    | multihash   | 0xb23f |                           |
   | blake2b-512    | multihash   | 0xb240 |                           |
   | blake2s-8      | multihash   | 0xb241 | Blake2s consists of 32    |
   |                |             |        | output lengths that give  |
   |                |             |        | different hashes          |
   | blake2s-16     | multihash   | 0xb242 |                           |
   | blake2s-24     | multihash   | 0xb243 |                           |
   | blake2s-32     | multihash   | 0xb244 |                           |
   | blake2s-40     | multihash   | 0xb245 |                           |
   | blake2s-48     | multihash   | 0xb246 |                           |
   | blake2s-56     | multihash   | 0xb247 |                           |
   | blake2s-64     | multihash   | 0xb248 |                           |
   | blake2s-72     | multihash   | 0xb249 |                           |
   | blake2s-80     | multihash   | 0xb24a |                           |
   | blake2s-88     | multihash   | 0xb24b |                           |
   | blake2s-96     | multihash   | 0xb24c |                           |
   | blake2s-104    | multihash   | 0xb24d |                           |
   | blake2s-112    | multihash   | 0xb24e |                           |
   | blake2s-120    | multihash   | 0xb24f |                           |
   | blake2s-128    | multihash   | 0xb250 |                           |
   | blake2s-136    | multihash   | 0xb251 |                           |
   | blake2s-144    | multihash   | 0xb252 |                           |
   | blake2s-152    | multihash   | 0xb253 |                           |
   | blake2s-160    | multihash   | 0xb254 |                           |
   | blake2s-168    | multihash   | 0xb255 |                           |
   | blake2s-176    | multihash   | 0xb256 |                           |
   | blake2s-184    | multihash   | 0xb257 |                           |



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   | blake2s-192    | multihash   | 0xb258 |                           |
   | blake2s-200    | multihash   | 0xb259 |                           |
   | blake2s-208    | multihash   | 0xb25a |                           |
   | blake2s-216    | multihash   | 0xb25b |                           |
   | blake2s-224    | multihash   | 0xb25c |                           |
   | blake2s-232    | multihash   | 0xb25d |                           |
   | blake2s-240    | multihash   | 0xb25e |                           |
   | blake2s-248    | multihash   | 0xb25f |                           |
   | blake2s-256    | multihash   | 0xb260 |                           |
   | skein256-8     | multihash   | 0xb301 | Skein256 consists of 32   |
   |                |             |        | output lengths that give  |
   |                |             |        | different hashes          |
   | skein256-16    | multihash   | 0xb302 |                           |
   | skein256-24    | multihash   | 0xb303 |                           |
   | skein256-32    | multihash   | 0xb304 |                           |
   | skein256-40    | multihash   | 0xb305 |                           |
   | skein256-48    | multihash   | 0xb306 |                           |
   | skein256-56    | multihash   | 0xb307 |                           |
   | skein256-64    | multihash   | 0xb308 |                           |
   | skein256-72    | multihash   | 0xb309 |                           |
   | skein256-80    | multihash   | 0xb30a |                           |
   | skein256-88    | multihash   | 0xb30b |                           |
   | skein256-96    | multihash   | 0xb30c |                           |
   | skein256-104   | multihash   | 0xb30d |                           |
   | skein256-112   | multihash   | 0xb30e |                           |
   | skein256-120   | multihash   | 0xb30f |                           |
   | skein256-128   | multihash   | 0xb310 |                           |
   | skein256-136   | multihash   | 0xb311 |                           |
   | skein256-144   | multihash   | 0xb312 |                           |
   | skein256-152   | multihash   | 0xb313 |                           |
   | skein256-160   | multihash   | 0xb314 |                           |
   | skein256-168   | multihash   | 0xb315 |                           |
   | skein256-176   | multihash   | 0xb316 |                           |
   | skein256-184   | multihash   | 0xb317 |                           |
   | skein256-192   | multihash   | 0xb318 |                           |
   | skein256-200   | multihash   | 0xb319 |                           |
   | skein256-208   | multihash   | 0xb31a |                           |
   | skein256-216   | multihash   | 0xb31b |                           |
   | skein256-224   | multihash   | 0xb31c |                           |
   | skein256-232   | multihash   | 0xb31d |                           |
   | skein256-240   | multihash   | 0xb31e |                           |
   | skein256-248   | multihash   | 0xb31f |                           |
   | skein256-256   | multihash   | 0xb320 |                           |
   | skein512-8     | multihash   | 0xb321 | Skein512 consists of 64   |
   |                |             |        | output lengths that give  |
   |                |             |        | different hashes          |
   | skein512-16    | multihash   | 0xb322 |                           |
   | skein512-24    | multihash   | 0xb323 |                           |



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   | skein512-32    | multihash   | 0xb324 |                           |
   | skein512-40    | multihash   | 0xb325 |                           |
   | skein512-48    | multihash   | 0xb326 |                           |
   | skein512-56    | multihash   | 0xb327 |                           |
   | skein512-64    | multihash   | 0xb328 |                           |
   | skein512-72    | multihash   | 0xb329 |                           |
   | skein512-80    | multihash   | 0xb32a |                           |
   | skein512-88    | multihash   | 0xb32b |                           |
   | skein512-96    | multihash   | 0xb32c |                           |
   | skein512-104   | multihash   | 0xb32d |                           |
   | skein512-112   | multihash   | 0xb32e |                           |
   | skein512-120   | multihash   | 0xb32f |                           |
   | skein512-128   | multihash   | 0xb330 |                           |
   | skein512-136   | multihash   | 0xb331 |                           |
   | skein512-144   | multihash   | 0xb332 |                           |
   | skein512-152   | multihash   | 0xb333 |                           |
   | skein512-160   | multihash   | 0xb334 |                           |
   | skein512-168   | multihash   | 0xb335 |                           |
   | skein512-176   | multihash   | 0xb336 |                           |
   | skein512-184   | multihash   | 0xb337 |                           |
   | skein512-192   | multihash   | 0xb338 |                           |
   | skein512-200   | multihash   | 0xb339 |                           |
   | skein512-208   | multihash   | 0xb33a |                           |
   | skein512-216   | multihash   | 0xb33b |                           |
   | skein512-224   | multihash   | 0xb33c |                           |
   | skein512-232   | multihash   | 0xb33d |                           |
   | skein512-240   | multihash   | 0xb33e |                           |
   | skein512-248   | multihash   | 0xb33f |                           |
   | skein512-256   | multihash   | 0xb340 |                           |
   | skein512-264   | multihash   | 0xb341 |                           |
   | skein512-272   | multihash   | 0xb342 |                           |
   | skein512-280   | multihash   | 0xb343 |                           |
   | skein512-288   | multihash   | 0xb344 |                           |
   | skein512-296   | multihash   | 0xb345 |                           |
   | skein512-304   | multihash   | 0xb346 |                           |
   | skein512-312   | multihash   | 0xb347 |                           |
   | skein512-320   | multihash   | 0xb348 |                           |
   | skein512-328   | multihash   | 0xb349 |                           |
   | skein512-336   | multihash   | 0xb34a |                           |
   | skein512-344   | multihash   | 0xb34b |                           |
   | skein512-352   | multihash   | 0xb34c |                           |
   | skein512-360   | multihash   | 0xb34d |                           |
   | skein512-368   | multihash   | 0xb34e |                           |
   | skein512-376   | multihash   | 0xb34f |                           |
   | skein512-384   | multihash   | 0xb350 |                           |
   | skein512-392   | multihash   | 0xb351 |                           |
   | skein512-400   | multihash   | 0xb352 |                           |
   | skein512-408   | multihash   | 0xb353 |                           |



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   | skein512-416   | multihash   | 0xb354 |                           |
   | skein512-424   | multihash   | 0xb355 |                           |
   | skein512-432   | multihash   | 0xb356 |                           |
   | skein512-440   | multihash   | 0xb357 |                           |
   | skein512-448   | multihash   | 0xb358 |                           |
   | skein512-456   | multihash   | 0xb359 |                           |
   | skein512-464   | multihash   | 0xb35a |                           |
   | skein512-472   | multihash   | 0xb35b |                           |
   | skein512-480   | multihash   | 0xb35c |                           |
   | skein512-488   | multihash   | 0xb35d |                           |
   | skein512-496   | multihash   | 0xb35e |                           |
   | skein512-504   | multihash   | 0xb35f |                           |
   | skein512-512   | multihash   | 0xb360 |                           |
   | skein1024-8    | multihash   | 0xb361 | Skein1024 consists of 128 |
   |                |             |        | output lengths that give  |
   |                |             |        | different hashes          |
   | skein1024-16   | multihash   | 0xb362 |                           |
   | skein1024-24   | multihash   | 0xb363 |                           |
   | skein1024-32   | multihash   | 0xb364 |                           |
   | skein1024-40   | multihash   | 0xb365 |                           |
   | skein1024-48   | multihash   | 0xb366 |                           |
   | skein1024-56   | multihash   | 0xb367 |                           |
   | skein1024-64   | multihash   | 0xb368 |                           |
   | skein1024-72   | multihash   | 0xb369 |                           |
   | skein1024-80   | multihash   | 0xb36a |                           |
   | skein1024-88   | multihash   | 0xb36b |                           |
   | skein1024-96   | multihash   | 0xb36c |                           |
   | skein1024-104  | multihash   | 0xb36d |                           |
   | skein1024-112  | multihash   | 0xb36e |                           |
   | skein1024-120  | multihash   | 0xb36f |                           |
   | skein1024-128  | multihash   | 0xb370 |                           |
   | skein1024-136  | multihash   | 0xb371 |                           |
   | skein1024-144  | multihash   | 0xb372 |                           |
   | skein1024-152  | multihash   | 0xb373 |                           |
   | skein1024-160  | multihash   | 0xb374 |                           |
   | skein1024-168  | multihash   | 0xb375 |                           |
   | skein1024-176  | multihash   | 0xb376 |                           |
   | skein1024-184  | multihash   | 0xb377 |                           |
   | skein1024-192  | multihash   | 0xb378 |                           |
   | skein1024-200  | multihash   | 0xb379 |                           |
   | skein1024-208  | multihash   | 0xb37a |                           |
   | skein1024-216  | multihash   | 0xb37b |                           |
   | skein1024-224  | multihash   | 0xb37c |                           |
   | skein1024-232  | multihash   | 0xb37d |                           |
   | skein1024-240  | multihash   | 0xb37e |                           |
   | skein1024-248  | multihash   | 0xb37f |                           |
   | skein1024-256  | multihash   | 0xb380 |                           |
   | skein1024-264  | multihash   | 0xb381 |                           |



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   | skein1024-272  | multihash   | 0xb382 |                           |
   | skein1024-280  | multihash   | 0xb383 |                           |
   | skein1024-288  | multihash   | 0xb384 |                           |
   | skein1024-296  | multihash   | 0xb385 |                           |
   | skein1024-304  | multihash   | 0xb386 |                           |
   | skein1024-312  | multihash   | 0xb387 |                           |
   | skein1024-320  | multihash   | 0xb388 |                           |
   | skein1024-328  | multihash   | 0xb389 |                           |
   | skein1024-336  | multihash   | 0xb38a |                           |
   | skein1024-344  | multihash   | 0xb38b |                           |
   | skein1024-352  | multihash   | 0xb38c |                           |
   | skein1024-360  | multihash   | 0xb38d |                           |
   | skein1024-368  | multihash   | 0xb38e |                           |
   | skein1024-376  | multihash   | 0xb38f |                           |
   | skein1024-384  | multihash   | 0xb390 |                           |
   | skein1024-392  | multihash   | 0xb391 |                           |
   | skein1024-400  | multihash   | 0xb392 |                           |
   | skein1024-408  | multihash   | 0xb393 |                           |
   | skein1024-416  | multihash   | 0xb394 |                           |
   | skein1024-424  | multihash   | 0xb395 |                           |
   | skein1024-432  | multihash   | 0xb396 |                           |
   | skein1024-440  | multihash   | 0xb397 |                           |
   | skein1024-448  | multihash   | 0xb398 |                           |
   | skein1024-456  | multihash   | 0xb399 |                           |
   | skein1024-464  | multihash   | 0xb39a |                           |
   | skein1024-472  | multihash   | 0xb39b |                           |
   | skein1024-480  | multihash   | 0xb39c |                           |
   | skein1024-488  | multihash   | 0xb39d |                           |
   | skein1024-496  | multihash   | 0xb39e |                           |
   | skein1024-504  | multihash   | 0xb39f |                           |
   | skein1024-512  | multihash   | 0xb3a0 |                           |
   | skein1024-520  | multihash   | 0xb3a1 |                           |
   | skein1024-528  | multihash   | 0xb3a2 |                           |
   | skein1024-536  | multihash   | 0xb3a3 |                           |
   | skein1024-544  | multihash   | 0xb3a4 |                           |
   | skein1024-552  | multihash   | 0xb3a5 |                           |
   | skein1024-560  | multihash   | 0xb3a6 |                           |
   | skein1024-568  | multihash   | 0xb3a7 |                           |
   | skein1024-576  | multihash   | 0xb3a8 |                           |
   | skein1024-584  | multihash   | 0xb3a9 |                           |
   | skein1024-592  | multihash   | 0xb3aa |                           |
   | skein1024-600  | multihash   | 0xb3ab |                           |
   | skein1024-608  | multihash   | 0xb3ac |                           |
   | skein1024-616  | multihash   | 0xb3ad |                           |
   | skein1024-624  | multihash   | 0xb3ae |                           |
   | skein1024-632  | multihash   | 0xb3af |                           |
   | skein1024-640  | multihash   | 0xb3b0 |                           |
   | skein1024-648  | multihash   | 0xb3b1 |                           |



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   | skein1024-656  | multihash   | 0xb3b2 |                           |
   | skein1024-664  | multihash   | 0xb3b3 |                           |
   | skein1024-672  | multihash   | 0xb3b4 |                           |
   | skein1024-680  | multihash   | 0xb3b5 |                           |
   | skein1024-688  | multihash   | 0xb3b6 |                           |
   | skein1024-696  | multihash   | 0xb3b7 |                           |
   | skein1024-704  | multihash   | 0xb3b8 |                           |
   | skein1024-712  | multihash   | 0xb3b9 |                           |
   | skein1024-720  | multihash   | 0xb3ba |                           |
   | skein1024-728  | multihash   | 0xb3bb |                           |
   | skein1024-736  | multihash   | 0xb3bc |                           |
   | skein1024-744  | multihash   | 0xb3bd |                           |
   | skein1024-752  | multihash   | 0xb3be |                           |
   | skein1024-760  | multihash   | 0xb3bf |                           |
   | skein1024-768  | multihash   | 0xb3c0 |                           |
   | skein1024-776  | multihash   | 0xb3c1 |                           |
   | skein1024-784  | multihash   | 0xb3c2 |                           |
   | skein1024-792  | multihash   | 0xb3c3 |                           |
   | skein1024-800  | multihash   | 0xb3c4 |                           |
   | skein1024-808  | multihash   | 0xb3c5 |                           |
   | skein1024-816  | multihash   | 0xb3c6 |                           |
   | skein1024-824  | multihash   | 0xb3c7 |                           |
   | skein1024-832  | multihash   | 0xb3c8 |                           |
   | skein1024-840  | multihash   | 0xb3c9 |                           |
   | skein1024-848  | multihash   | 0xb3ca |                           |
   | skein1024-856  | multihash   | 0xb3cb |                           |
   | skein1024-864  | multihash   | 0xb3cc |                           |
   | skein1024-872  | multihash   | 0xb3cd |                           |
   | skein1024-880  | multihash   | 0xb3ce |                           |
   | skein1024-888  | multihash   | 0xb3cf |                           |
   | skein1024-896  | multihash   | 0xb3d0 |                           |
   | skein1024-904  | multihash   | 0xb3d1 |                           |
   | skein1024-912  | multihash   | 0xb3d2 |                           |
   | skein1024-920  | multihash   | 0xb3d3 |                           |
   | skein1024-928  | multihash   | 0xb3d4 |                           |
   | skein1024-936  | multihash   | 0xb3d5 |                           |
   | skein1024-944  | multihash   | 0xb3d6 |                           |
   | skein1024-952  | multihash   | 0xb3d7 |                           |
   | skein1024-960  | multihash   | 0xb3d8 |                           |
   | skein1024-968  | multihash   | 0xb3d9 |                           |
   | skein1024-976  | multihash   | 0xb3da |                           |
   | skein1024-984  | multihash   | 0xb3db |                           |
   | skein1024-992  | multihash   | 0xb3dc |                           |
   | skein1024-1000 | multihash   | 0xb3dd |                           |
   | skein1024-1008 | multihash   | 0xb3de |                           |
   | skein1024-1016 | multihash   | 0xb3df |                           |
   | skein1024-1024 | multihash   | 0xb3e0 |                           |
   +----------------+-------------+--------+---------------------------+



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   For each of the above entries, this document serves as the reference.

6.2.  The Multibase Registry

6.2.1.  Base-Encoding Registration

   Base-encoding identifiers can be registered using the procedure
   described herein.

   Base-encodings are registered using the Expert Review policy (see
   Section 4.5 of [RFC8126]).  The goal of the registry is to reflect
   common use of codecs on the Internet.  Therefore, the expert(s)
   should be strongly biased towards approving registrations, unless
   they are abusive, frivolous, not likely to be used on the Internet,
   or actively harmful to the Internet and/or the Web (not merely
   aesthetically displeasing or architecturally dubious).  Expert(s) can
   withhold registration of codecs that are too general for the proposal
   application.

   Expert(s) will clearly identify any issues that cause a registration
   to be refused.  Advice about the semantics of a proposed codec can be
   given, but if it does not block registration, this should be
   explicitly stated.

   When a request if approved, the expert(s) shall inform IANA, and the
   regstration will be processed.  The IESG is the final arbiter of any
   objection.

   The Multibase Registry is located at
   https://www.iana.org/assignments/multiformat-base.  Registration
   requests can be made by following instructions located there or by
   sending an email to the multiformat-codecs@ietf.org mailing list.

   Registration requests consist of at least the following information:

   o  *Name*: The name of base-encoding

   o  *Prefix*: The requested prefix identifier

   o  *Description*: An optional short text description of the base
      encoding.

   o  *Status*: An indicator of the current implementation status of the
      encoding and prefix.  MUST be one of "draft", "candidate", or
      "default".

   o  *Reference*: A reference to the document that specifies the base
      encoding, preferably including a URI that can be used to retrieve



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      a copy of the document.  An indication of the relevant section(s)
      can also be included but is not required.

   Each of the Status field values indicates the following meanings:

   o  *draft*: The encoding has been proposed but is not widely
      implemented and may be removed in the future.

   o  *candidate*: The encoding is mature and widely implemented by many
      but not all implementations.

   o  *default*: The encoding SHOULD be implemented by all
      implementations and are widely used.

   The expert(s) can change the Status of a registration at any time.

   The expert(s) can define additional fields to be collected in the
   registry.

   Registrations SHOULD reference a freely available, stable
   specification.

   Note that base encoding can be registered by third parties (including
   the expert(s)), if the expert(s) determine that an unregistered base
   encoding is widely deployed and not likely to be registered in a
   timely manner otherwise.  Such registrations still are subject to the
   requirements defined.

6.2.2.  Initial Contents

   The initial contents of the Multibase Registry are as follows:




















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   +-------------------+------+----------------------------+-----------+
   | Encoding          | Code | Description                | Status    |
   +-------------------+------+----------------------------+-----------+
   | identity          | 0x00 | 8-bit binary (encoder and  | default   |
   |                   |      | decoder keeps data         |           |
   |                   |      | unmodified)                |           |
   | base2             | 0    | binary (01010101)          | candidate |
   | base8             | 7    | octal                      | draft     |
   | base10            | 9    | decimal                    | draft     |
   | base16            | f    | hexadecimal                | default   |
   | base16upper       | F    | hexadecimal                | default   |
   | base32hex         | v    | rfc4648 no padding -       | candidate |
   |                   |      | highest char               |           |
   | base32hexupper    | V    | rfc4648 no padding -       | candidate |
   |                   |      | highest char               |           |
   | base32hexpad      | t    | rfc4648 with padding       | candidate |
   | base32hexpadupper | T    | rfc4648 with padding       | candidate |
   | base32            | b    | rfc4648 no padding         | default   |
   | base32upper       | B    | rfc4648 no padding         | default   |
   | base32pad         | c    | rfc4648 with padding       | candidate |
   | base32padupper    | C    | rfc4648 with padding       | candidate |
   | base32z           | h    | z-base-32 (used by Tahoe-  | draft     |
   |                   |      | LAFS)                      |           |
   | base58flickr      | Z    | base58 flicker             | candidate |
   | base58btc         | z    | base58 bitcoin             | default   |
   | base64            | m    | rfc4648 no padding         | default   |
   | base64pad         | M    | rfc4648 with padding -     | candidate |
   |                   |      | MIME encoding              |           |
   | base64url         | u    | rfc4648 no padding         | default   |
   | base64urlpad      | U    | rfc4648 with padding       | default   |
   +-------------------+------+----------------------------+-----------+

   For each of the above entries, this document serves as the reference.

7.  Normative References

   [LEB128]   DWARF Debugging Information Format Workgroup, "DWARF
              Debugging Information Format", December 2005,
              <http://dwarfstd.org/doc/Dwarf3.pdf>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.







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   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

Authors' Addresses

   James M Snell (editor)
   NearForm Research

   Email: jasnell@gmail.com


   Nicola Greco
   Protocol Labs

   Email: me@nicola.io


   Juan Benet
   Protocol Labs

   Email: juan@benet.ai


   David A. Dalrymple
   Protocol Labs

   Email: david.dalrymple@protocol.ai


   David Dias
   Protocol Labs

   Email: mail@daviddias.me


   Lars Gierth
   Protocol Labs

   Email: lars.gierth@gmail.com





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