RFC 7479

RFC 7479: Using Ed25519 in SSHFP Resource Records 🦋

Bestie, here's the title block tea ☕

• Published by: the Internet Engineering Task Force (IETF) 🌸
• Author: S. Moonesamy 🎀
• Date: March 2015 📅
• Category: Informational, so it's sharing info, not a Standards Track spec 💅
• ISSN: 2070-1721
• Obsoletes: nothing listed 🙅
• Updates: no RFCs listed, but it does update the IANA "SSHFP RR Types for public key algorithms" registry ✨

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Abstract ✨

okay so the Ed25519 signature algorithm is already implemented in OpenSSH 🔥 and this doc updates the IANA "SSHFP RR Types for public key algorithms" registry by adding an algorithm number for Ed25519. iconic, honestly 👑

Status of This Memo 📜

This document is not an Internet Standards Track specification. It's published for informational purposes 💖

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard, see Section 2 of RFC 5741. Not every approved doc is standards material, bestie 🙈

Info about the current status of this document, any errata, and how to give feedback on it lives at http://www.rfc-editor.org/info/rfc7479 🧚

Copyright Notice ⚖️

Copyright (c) 2015 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, since they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions, and they are provided without warranty as described in the Simplified BSD License 🫶

Table of Contents 🗺️

1. Introduction ....................................................2
2. Ed25519 Public Key with SHA-256 Fingerprint .....................2
3. Security Considerations .........................................3
4. IANA Considerations .............................................3
5. References ......................................................3
   5.1. Normative References .......................................3
   5.2. Informative References .....................................3
Acknowledgements ...................................................4
Author's Address ...................................................4

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1. Introduction 🌸

okay so the Ed25519 [Ed25519] signature algorithm, specifically Ed25519-SHA-512, is implemented in OpenSSH. RFC 4255 [RFC4255] defines a DNS resource record called "SSHFP", which can be used to publish a fingerprint of the SSH server public key in the DNS 🔐

This document updates the IANA "SSHFP RR Types for public key algorithms" registry by adding an algorithm number for Ed25519 [Ed25519]. main character energy 💅

2. Ed25519 Public Key with SHA-256 Fingerprint 🔑

The encoding of Ed25519 public keys is described in [Ed25519]. The quick version: an Ed25519 public key is a 32-octet value. It represents a 255-bit y-coordinate of an elliptic curve point, plus a sign bit that tells you which x-coordinate goes with it 🧮

The SSHFP Resource Record for the Ed25519 public key with SHA-256 fingerprint [FIPS180-4] would, for example, look like this 🍓

   ssh.example.com IN SSHFP 4 2 ( a87f1b687ac0e57d2a081a2f2826723
                                  34d90ed316d2b818ca9580ea384d924
                                  01 )

The following body of the public key file was used as input to generate the above fingerprint 🦋

 ssh-ed25519
 AAAAC3NzaC1lZDI1NTE5AAAAIGPKSUTyz1HwHReFVvD5obVsALAgJRNarH4TRpNePnAS

The opaque octet string output produced gets placed as is in the RDATA fingerprint field. no edits, no vibes-based changes 🫶

3. Security Considerations 🚨

Bestie, this part is SERIOUS, so read it carefully 🙏

The overall security of using SSHFP for SSH host key verification depends on a few things. It depends on the security policies of the SSH host administrator and the DNS zone administrator (in transferring the fingerprint). It also depends on the detailed aspects of how verification is done in the SSH implementation, and on the client's diligence in accessing the DNS in a secure manner.

Please refer to RFC 4255 [RFC4255] for a discussion of the security considerations 💖

4. IANA Considerations 🧚

IANA has added the following entry to the "SSHFP RR Types for public key algorithms" registry 📋

   +--------+-------------+------------+
   | Value  | Description |  Reference |
   +--------+-------------+------------+
   |   4    |    Ed25519  | [RFC7479]  |
   +--------+-------------+------------+

5. References 📚

5.1. Normative References

[Ed25519]    Bernstein, D. J., Lange T., Schwabe P., and B-Y. Yang,
             "High-Speed High-Security Signatures", Journal of
             Cryptographic Engineering, Vol. 2, September 26, 2011.

[RFC4255]    Schlyter, J. and W. Griffin, "Using DNS to Securely
             Publish Secure Shell (SSH) Key Fingerprints", RFC 4255,
             January 2006, <http://www.rfc-editor.org/info/rfc4255>.

5.2. Informative References

[FIPS180-4]  National Institute of Standards and Technology, "Secure
             Hash Standard (SHS)", FIPS PUB 180-4, March 2012,
             <http://csrc.nist.gov/publications/fips/fips180-4/
             fips-180-4.pdf>.

Acknowledgements 🫶

Some of the text in this document was written by Ondrej Sury. The author would like to thank Richard Barnes, Damien Miller, Yoav Nir, and Paul Wouters for their feedback. Rene Struik provided advice about the usage of Ed25519. Stephen Farrell, as Security Area Director, reviewed the code point request. the group chat really came through for this one 💜

Author's Address 💌

S. Moonesamy
76, Ylang Ylang Avenue
Quatres Bornes
Mauritius

EMail: sm+ietf@elandsys.com