The Multibase Data Format

Status of This Memo

This Internet-Draft is submitted 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-Drafts is at https://datatracker.ietf.org/drafts/current/.¶

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 21 February 2024.¶

Copyright Notice

Copyright (c) 2023 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. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶

Table of Contents

1. Introduction

This specification describes a forward-compatible data model for expressing raw binary data in a variety of base-encoding formats such as base32, base58. and base64.¶

When text is encoded as bytes, we can usually use a one-size-fits-all encoding (UTF-8) because we're always encoding to the same set of 256 bytes. When that doesn't work, usually for historical or performance reasons, we can usually infer the encoding from the context.¶

However, when bytes are encoded as text (using a base encoding), the choice of base encoding is often restricted by the context. Worse, these restrictions can change based on where the data appears in the text. In some cases, we can only use [a-z0-9]. In others, we can use a larger set of characters but need a compact encoding. This has lead to a large set of "base encodings", one for every use-case. Unlike when encoding text to bytes, we can't just standardize around a single base encoding because there is no optimal encoding for all cases.¶

Unfortunately, it's not always clear what base encoding is used; that's where this specification comes in. It answers the question:¶

Given data 'd' encoded into text 's', what base is it encoded with?¶

2. The Multibase Format

A multibase-encoded value follows a simple format:¶

base-encoding-character base-encoded-data

The encoding algorithm is a single character value that is always the first byte of the data. The possible values for this field are provided in The Multibase Algorithm Registry.¶

z2NEpo7TZRRrLZSi2U

Appendix A. Security Considerations

There are a number of security considerations to take into account when implementing or utilizing this specification. TBD¶

Appendix B. Test Values

The multibase examples are chosen to show different encoding algorithms and different output lengths at play. The input test data for all of the examples in this section is:¶

Multibase is awesome! \o/

F4D756C74696261736520697320617765736F6D6521205C6F2F

BJV2WY5DJMJQXGZJANFZSAYLXMVZW63LFEEQFY3ZP

zYAjKoNbau5KiqmHPmSxYCvn66dA1vLmwbt

MTXVsdGliYXNlIGlzIGF3ZXNvbWUhIFxvLw==

Appendix C. Acknowledgements

The editors would like to thank the following individuals for feedback on and implementations of the specification (in alphabetical order):¶

Appendix D. IANA Considerations

Authors' Addresses