



Internet Engineering Task Force                                B. Harris
Internet-Draft
Updates: RFC4253 (if approved)                             L. Velvindron
Intended status: Standards Track                           cyberstorm.mu
Expires: March 12, 2020                                September 9, 2019


   Ed25519 and Ed448 public key algorithms for the Secure Shell (SSH)
                                protocol
                 draft-ietf-curdle-ssh-ed25519-ed448-11

Abstract

   This document describes the use of the Ed25519 and Ed448 digital
   signature algorithm in the Secure Shell (SSH) protocol.

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
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   This Internet-Draft will expire on March 12, 2020.

Copyright Notice

   Copyright (c) 2019 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
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   described in the Simplified BSD License.




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1.  Introduction

   Secure Shell (SSH) [RFC4251] is a secure remote-login protocol.  It
   provides for an extensible variety of public key algorithms for
   identifying servers and users to one another.  Ed25519 [RFC8032] is a
   digital signature system.  OpenSSH 6.5 [OpenSSH-6.5] introduced
   support for using Ed25519 for server and user authentication and was
   then followed by other SSH implementations.

   This document describes the method implemented by OpenSSH and others,
   and formalizes its use of the name "ssh-ed25519".  Additionally, it
   also describes the use of Ed448 and formalizes its use of the name
   "ssh-ed448".

   [TO BE REMOVED: Please send comments on this draft to
   curdle@ietf.org.]

2.  Conventions Used in This Document

   The descriptions of key and signature formats use the notation
   introduced in [RFC4251], Section 3 [RFC4251] and the string data type
   from [RFC4251], Section 5 [RFC4251].

2.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119] RFC
   8174 [RFC8174] when, and only when, they appear in all capitals, as
   shown here.

3.  Public Key Algorithm

   This document describes a public key algorithm for use with SSH in
   accordance with [RFC4253], Section 6.6 [RFC4253].  The name of the
   algorithm is "ssh-ed25519".  This algorithm only supports signing and
   not encryption.

   Additionally, this document describes another public key algorithm.
   The name of the algorithm is "ssh-ed448".  This algorithm only
   supports signing and not encryption.

   Standard implementations of SSH SHOULD implement these signature
   algorithms.







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4.  Public Key Format

   The "ssh-ed25519" key format has the following encoding:

   string    "ssh-ed25519"
   string    key

   Here 'key' is the 32-octet public key described by [RFC8032],
   Section 5.1.5 [RFC8032].

   The "ssh-ed448" key format has the following encoding:

   string    "ssh-ed448"
   string    key

   Here 'key' is the 57-octet public key described by [RFC8032],
   Section 5.2.5 [RFC8032].

5.  Signature Algorithm

   Signatures are generated according to the procedure in [RFC8032],
   Section 5.1.6 and Section 5.2.6 [RFC8032].

6.  Signature Format

   The "ssh-ed25519" key format has the following encoding:

   string    "ssh-ed25519"
   string    signature

   Here 'signature' is the 64-octet signature produced in accordance
   with [RFC8032], Section 5.1.6 [RFC8032].

   The "ssh-ed448" key format has the following encoding:

   string    "ssh-ed448"
   string    signature

   Here 'signature' is the 114-octet signature produced in accordance
   with [RFC8032], Section 5.2.6 [RFC8032].

7.  Verification Algorithm

   Ed25519 signatures are verified according to the procedure in
   [RFC8032], Section 5.1.7 [RFC8032].

   Ed448 signatures are verified according to the procedure in
   [RFC8032], Section 5.2.7 [RFC8032].



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8.  SSHFP DNS resource records

   Usage and generation of SSHFP DNS resource record is described in
   [RFC4255].  The generation of SSHFP resource records for "ssh-
   ed25519" keys is described in [RFC7479].  This section illustrates
   the generation of SSHFP resource records for "ssh-ed448" keys and the
   document specifies the corresponding Ed448 code point to the "SSHFP
   RR Types for public key algorithms" IANA registry.

   The generation of SSHFP resource records for "ssh-ed25519" keys is
   described in [RFC7479].

   The generation of SSHFP resource records for "ssh-ed448" keys is
   described as follows.

   The encoding of Ed448 public keys is described in [ED448].  In brief,
   an Ed448 public key is a 57-octet value representing a 455-bit
   y-coordinate of an elliptic curve point, and a sign bit indicating
   the the corresponding x-coordinate.

   The SSHFP Resource Record for the Ed448 public key with SHA-256
   fingerprint would for example be:

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

   The 2 here indicates SHA-256 [RFC6594].

9.  IANA Considerations

   This document augments the Public Key Algorithm Names in [RFC4250],
   Section 4.6.2 [RFC4250].

   IANA is requested to add to the Public Key Algorithm Names registry
   [IANA-PKA] with the following entry:

                   Public Key Algorithm Name Reference
                   ------------------------- ----------
                   ssh-ed25519               This Draft
                   ssh-ed448                 This Draft

   IANA is requested to add the following entry to the "SSHFP RR Types
   for public key algorithms" registry [IANA-SSHFP]:

   +--------+-------------+------------+

   | Value | Description | Reference |




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   +--------+-------------+------------+

   | TBD | Ed448 | [this-draft] |

   +--------+-------------+------------+

   We strongly suggest 6 as value.

   [TO BE REMOVED: This registration should take place at the following
   location: <http://www.iana.org/assignments/ssh-parameters/ssh-
   parameters.xhtml#ssh-parameters-19>]

10.  Security Considerations

   The security considerations in [RFC4251], Section 9 [RFC4251] apply
   to all SSH implementations, including those using Ed25519 and Ed448.

   The security considerations in [RFC8032], Section 8 [RFC8032] and
   [RFC7479] apply to all uses of Ed25519 and Ed448 including those in
   SSH.

11.  Acknowledgements

   The OpenSSH implementation of Ed25519 in SSH was written by Markus
   Friedl.  We are also grateful to Mark Baushke, Benjamin Kaduk and
   Daniel Migault for their comments.

12.  References

12.1.  Normative References

   [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>.

   [RFC4250]  Lehtinen, S. and C. Lonvick, Ed., "The Secure Shell (SSH)
              Protocol Assigned Numbers", RFC 4250,
              DOI 10.17487/RFC4250, January 2006,
              <https://www.rfc-editor.org/info/rfc4250>.

   [RFC4251]  Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
              Protocol Architecture", RFC 4251, DOI 10.17487/RFC4251,
              January 2006, <https://www.rfc-editor.org/info/rfc4251>.

   [RFC4253]  Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
              Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253,
              January 2006, <https://www.rfc-editor.org/info/rfc4253>.



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   [RFC4255]  Schlyter, J. and W. Griffin, "Using DNS to Securely
              Publish Secure Shell (SSH) Key Fingerprints", RFC 4255,
              DOI 10.17487/RFC4255, January 2006,
              <https://www.rfc-editor.org/info/rfc4255>.

   [RFC6594]  Sury, O., "Use of the SHA-256 Algorithm with RSA, Digital
              Signature Algorithm (DSA), and Elliptic Curve DSA (ECDSA)
              in SSHFP Resource Records", RFC 6594,
              DOI 10.17487/RFC6594, April 2012,
              <https://www.rfc-editor.org/info/rfc6594>.

   [RFC8032]  Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
              Signature Algorithm (EdDSA)", RFC 8032,
              DOI 10.17487/RFC8032, January 2017,
              <https://www.rfc-editor.org/info/rfc8032>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

12.2.  Informative References

   [ED448]    Hamburg, M., "Ed448-Goldilocks, a new elliptic curve",
              January 2015, <https://eprint.iacr.org/2015/625.pdf>.

   [IANA-PKA]
              Internet Assigned Numbers Authority (IANA), "Secure Shell
              (SSH) Protocol Parameters: Public Key Algorithm Names",
              May 2017, <http://www.iana.org/assignments/ssh-parameters/
              ssh-parameters.xhtml#ssh-parameters-19>.

   [IANA-SSHFP]
              Internet Assigned Numbers Authority (IANA), "Secure Shell
              (SSH) Protocol Parameters: Public Key Algorithm Names",
              May 2017, <https://www.iana.org/assignments/dns-sshfp-rr-
              parameters/
              dns-sshfp-rr-parameters.xhtml#dns-sshfp-rr-parameters-1>.

   [OpenSSH-6.5]
              Friedl, M., Provos, N., de Raadt, T., Steves, K., Miller,
              D., Tucker, D., Rice, T., and B. Lindstrom, "OpenSSH 6.5
              release notes", January 2014,
              <http://www.openssh.com/txt/release-6.5>.

   [RFC7479]  Moonesamy, S., "Using Ed25519 in SSHFP Resource Records",
              RFC 7479, DOI 10.17487/RFC7479, March 2015,
              <https://www.rfc-editor.org/info/rfc7479>.




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Authors' Addresses

   Ben Harris
   2A Eachard Road
   CAMBRIDGE  CB3 0HY
   UNITED KINGDOM

   Email: bjh21@bjh21.me.uk


   Loganaden Velvindron
   cyberstorm.mu
   88, Avenue De Plevitz
   Roches Brunes
   Mauritius

   Email: logan@cyberstorm.mu


































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