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Internet Engineering Task Force (IETF)                      S. MoonesamyRequest for Comments: 7479                                    March 2015Category: InformationalISSN: 2070-1721Using Ed25519 in SSHFP Resource RecordsAbstract   The Ed25519 signature algorithm has been implemented in OpenSSH.   This document updates the IANA "SSHFP RR Types for public key   algorithms" registry by adding an algorithm number for Ed25519.Status of This Memo   This document is not an Internet Standards Track specification; it is   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; seeSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://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 toBCP 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, as 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 are provided without warranty as   described in the Simplified BSD License.Moonesamy                     Informational                     [Page 1]

RFC 7479               Using Ed25519 in SSHFP RRs             March 2015Table of Contents1. Introduction ....................................................22. Ed25519 Public Key with SHA-256 Fingerprint .....................23. Security Considerations .........................................34. IANA Considerations .............................................35. References ......................................................35.1. Normative References .......................................35.2. Informative References .....................................3   Acknowledgements ...................................................4   Author's Address ...................................................41.  Introduction   The Ed25519 [Ed25519] signature algorithm, specifically   Ed25519-SHA-512, has been implemented in OpenSSH.RFC 4255 [RFC4255]   defines a DNS resource record, "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].2.  Ed25519 Public Key with SHA-256 Fingerprint   The encoding of Ed25519 public keys is described in [Ed25519].  In   brief, an Ed25519 public key is a 32-octet value representing a   255-bit y-coordinate of an elliptic curve point, and a sign bit   indicating the corresponding x-coordinate.   The SSHFP Resource Record for the Ed25519 public key with SHA-256   fingerprint [FIPS180-4] would, for example, be:      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 is placed as is in the RDATA   fingerprint field.Moonesamy                     Informational                     [Page 2]

RFC 7479               Using Ed25519 in SSHFP RRs             March 20153.  Security Considerations   The overall security of using SSHFP for SSH host key verification is   dependent on the security policies of the SSH host administrator and   DNS zone administrator (in transferring the fingerprint), detailed   aspects of how verification is done in the SSH implementation, and in   the client's diligence in accessing the DNS in a secure manner.   Please refer toRFC 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.  References5.1.  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>.Moonesamy                     Informational                     [Page 3]

RFC 7479               Using Ed25519 in SSHFP RRs             March 2015Acknowledgements   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.Author's Address   S. Moonesamy   76, Ylang Ylang Avenue   Quatres Bornes   Mauritius   EMail: sm+ietf@elandsys.comMoonesamy                     Informational                     [Page 4]