draft-ietf-curdle-ssh-ed25519-ed448-11.txt   rfc8709.txt 
Internet Engineering Task Force B. Harris Internet Engineering Task Force (IETF) B. Harris
Internet-Draft Request for Comments: 8709
Updates: RFC4253 (if approved) L. Velvindron Updates: 4253 L. Velvindron
Intended status: Standards Track cyberstorm.mu Category: Standards Track cyberstorm.mu
Expires: March 12, 2020 September 9, 2019 ISSN: 2070-1721 February 2020
Ed25519 and Ed448 public key algorithms for the Secure Shell (SSH) Ed25519 and Ed448 Public Key Algorithms for the Secure Shell (SSH)
protocol Protocol
draft-ietf-curdle-ssh-ed25519-ed448-11
Abstract Abstract
This document describes the use of the Ed25519 and Ed448 digital This document describes the use of the Ed25519 and Ed448 digital
signature algorithm in the Secure Shell (SSH) protocol. signature algorithms in the Secure Shell (SSH) protocol.
Accordingly, this RFC updates RFC 4253.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
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Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on March 12, 2020. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8709.
Copyright Notice Copyright Notice
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document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents
1. Introduction
2. Conventions Used in This Document
2.1. Requirements Language
3. Public Key Algorithm
4. Public Key Format
5. Signature Algorithm
6. Signature Format
7. Verification Algorithm
8. SSHFP DNS Resource Records
9. IANA Considerations
10. Security Considerations
11. References
11.1. Normative References
11.2. Informative References
Acknowledgements
Authors' Addresses
1. Introduction 1. Introduction
Secure Shell (SSH) [RFC4251] is a secure remote-login protocol. It Secure Shell (SSH) [RFC4251] is a secure remote-login protocol. It
provides for an extensible variety of public key algorithms for provides for an extensible variety of public key algorithms for
identifying servers and users to one another. Ed25519 [RFC8032] is a identifying servers and users to one another. Ed25519 [RFC8032] is a
digital signature system. OpenSSH 6.5 [OpenSSH-6.5] introduced digital signature system. OpenSSH 6.5 [OpenSSH-6.5] introduced
support for using Ed25519 for server and user authentication and was support for using Ed25519 for server and user authentication and was
then followed by other SSH implementations. then followed by other SSH implementations.
This document describes the method implemented by OpenSSH and others, This document describes the method implemented by OpenSSH and others
and formalizes its use of the name "ssh-ed25519". Additionally, it and formalizes the use of the name "ssh-ed25519". Additionally, this
also describes the use of Ed448 and formalizes its use of the name document describes the use of Ed448 and formalizes the use of the
"ssh-ed448". name "ssh-ed448".
[TO BE REMOVED: Please send comments on this draft to
curdle@ietf.org.]
2. Conventions Used in This Document 2. Conventions Used in This Document
The descriptions of key and signature formats use the notation The descriptions of key and signature formats use the notation
introduced in [RFC4251], Section 3 [RFC4251] and the string data type introduced in [RFC4251], Section 3 and the string data type from
from [RFC4251], Section 5 [RFC4251]. [RFC4251], Section 5.
2.1. Requirements Language 2.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in RFC 2119 [RFC2119] RFC "OPTIONAL" in this document are to be interpreted as described in
8174 [RFC8174] when, and only when, they appear in all capitals, as BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
shown here. capitals, as shown here.
3. Public Key Algorithm 3. Public Key Algorithm
This document describes a public key algorithm for use with SSH in This document describes a public key algorithm for use with SSH, as
accordance with [RFC4253], Section 6.6 [RFC4253]. The name of the per [RFC4253], Section 6.6. The name of the algorithm is "ssh-
algorithm is "ssh-ed25519". This algorithm only supports signing and ed25519". This algorithm only supports signing and not encryption.
not encryption.
Additionally, this document describes another public key algorithm. Additionally, this document describes another public key algorithm.
The name of the algorithm is "ssh-ed448". This algorithm only The name of the algorithm is "ssh-ed448". This algorithm only
supports signing and not encryption. supports signing and not encryption.
Standard implementations of SSH SHOULD implement these signature Standard implementations of SSH SHOULD implement these signature
algorithms. algorithms.
4. Public Key Format 4. Public Key Format
The "ssh-ed25519" key format has the following encoding: The "ssh-ed25519" key format has the following encoding:
string "ssh-ed25519" string "ssh-ed25519"
string key
Here 'key' is the 32-octet public key described by [RFC8032], string key
Section 5.1.5 [RFC8032].
Here, 'key' is the 32-octet public key described in [RFC8032],
Section 5.1.5.
The "ssh-ed448" key format has the following encoding: The "ssh-ed448" key format has the following encoding:
string "ssh-ed448" string "ssh-ed448"
string key
Here 'key' is the 57-octet public key described by [RFC8032], string key
Section 5.2.5 [RFC8032].
Here, 'key' is the 57-octet public key described in [RFC8032],
Section 5.2.5.
5. Signature Algorithm 5. Signature Algorithm
Signatures are generated according to the procedure in [RFC8032], Signatures are generated according to the procedure in Sections 5.1.6
Section 5.1.6 and Section 5.2.6 [RFC8032]. and 5.2.6 of [RFC8032].
6. Signature Format 6. Signature Format
The "ssh-ed25519" key format has the following encoding: The "ssh-ed25519" key format has the following encoding:
string "ssh-ed25519" string "ssh-ed25519"
string signature
Here 'signature' is the 64-octet signature produced in accordance string signature
with [RFC8032], Section 5.1.6 [RFC8032].
Here, 'signature' is the 64-octet signature produced in accordance
with [RFC8032], Section 5.1.6.
The "ssh-ed448" key format has the following encoding: The "ssh-ed448" key format has the following encoding:
string "ssh-ed448" string "ssh-ed448"
string signature
Here 'signature' is the 114-octet signature produced in accordance string signature
with [RFC8032], Section 5.2.6 [RFC8032].
Here, 'signature' is the 114-octet signature produced in accordance
with [RFC8032], Section 5.2.6.
7. Verification Algorithm 7. Verification Algorithm
Ed25519 signatures are verified according to the procedure in Ed25519 signatures are verified according to the procedure in
[RFC8032], Section 5.1.7 [RFC8032]. [RFC8032], Section 5.1.7.
Ed448 signatures are verified according to the procedure in Ed448 signatures are verified according to the procedure in
[RFC8032], Section 5.2.7 [RFC8032]. [RFC8032], Section 5.2.7.
8. SSHFP DNS resource records 8. SSHFP DNS Resource Records
Usage and generation of SSHFP DNS resource record is described in Usage and generation of the SSHFP DNS resource record is described in
[RFC4255]. The generation of SSHFP resource records for "ssh- [RFC4255]. The generation of SSHFP resource records for "ssh-
ed25519" keys is described in [RFC7479]. This section illustrates ed25519" keys is described in [RFC7479]. This section illustrates
the generation of SSHFP resource records for "ssh-ed448" keys and the the generation of SSHFP resource records for "ssh-ed448" keys, and
document specifies the corresponding Ed448 code point to the "SSHFP this document also specifies the corresponding Ed448 code point to
RR Types for public key algorithms" IANA registry. "SSHFP RR Types for public key algorithms" in the "DNS SSHFP Resource
Record Parameters" IANA registry [IANA-SSHFP].
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 The generation of SSHFP resource records for "ssh-ed448" keys is
described as follows. described as follows.
The encoding of Ed448 public keys is described in [ED448]. In brief, 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 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 y-coordinate of an elliptic curve point, and a sign bit indicating
the the corresponding x-coordinate. the corresponding x-coordinate.
The SSHFP Resource Record for the Ed448 public key with SHA-256 The SSHFP Resource Record for the Ed448 public key with SHA-256
fingerprint would for example be: fingerprint would, for example, be:
example.com. IN SSHFP TBD 2 ( a87f1b687ac0e57d2a081a2f2826723 example.com. IN SSHFP 6 2 ( a87f1b687ac0e57d2a081a2f2826723
34d90ed316d2b818ca9580ea384d924 01 ) 34d90ed316d2b818ca9580ea384d924
01 )
The 2 here indicates SHA-256 [RFC6594]. The '2' here indicates SHA-256 [RFC6594].
9. IANA Considerations 9. IANA Considerations
This document augments the Public Key Algorithm Names in [RFC4250], This document augments the Public Key Algorithm Names in [RFC4250],
Section 4.6.2 [RFC4250]. Section 4.11.3.
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]:
+--------+-------------+------------+ IANA has added the following entry to "Public Key Algorithm Names" in
the "Secure Shell (SSH) Protocol Parameters" registry [IANA-SSH]:
| Value | Description | Reference | +---------------------------+-----------+
+--------+-------------+------------+ | Public Key Algorithm Name | Reference |
+===========================+===========+
| ssh-ed25519 | RFC 8709 |
+---------------------------+-----------+
| ssh-ed448 | RFC 8709 |
+---------------------------+-----------+
| TBD | Ed448 | [this-draft] | Table 1
+--------+-------------+------------+ IANA has added the following entry to "SSHFP RR Types for public key
algorithms" in the "DNS SSHFP Resource Record Parameters" registry
[IANA-SSHFP]:
We strongly suggest 6 as value. +-------+-------------+-----------+
| Value | Description | Reference |
+=======+=============+===========+
| 6 | Ed448 | RFC 8709 |
+-------+-------------+-----------+
[TO BE REMOVED: This registration should take place at the following Table 2
location: <http://www.iana.org/assignments/ssh-parameters/ssh-
parameters.xhtml#ssh-parameters-19>]
10. Security Considerations 10. Security Considerations
The security considerations in [RFC4251], Section 9 [RFC4251] apply The security considerations in [RFC4251], Section 9 apply to all SSH
to all SSH implementations, including those using Ed25519 and Ed448. implementations, including those using Ed25519 and Ed448.
The security considerations in [RFC8032], Section 8 [RFC8032] and The security considerations in [RFC8032], Section 8 and [RFC7479],
[RFC7479] apply to all uses of Ed25519 and Ed448 including those in Section 3 apply to all uses of Ed25519 and Ed448, including those in
SSH. SSH.
11. Acknowledgements 11. References
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 11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4250] Lehtinen, S. and C. Lonvick, Ed., "The Secure Shell (SSH) [RFC4250] Lehtinen, S. and C. Lonvick, Ed., "The Secure Shell (SSH)
Protocol Assigned Numbers", RFC 4250, Protocol Assigned Numbers", RFC 4250,
DOI 10.17487/RFC4250, January 2006, DOI 10.17487/RFC4250, January 2006,
<https://www.rfc-editor.org/info/rfc4250>. <https://www.rfc-editor.org/info/rfc4250>.
skipping to change at page 6, line 25 skipping to change at line 267
[RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital [RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
Signature Algorithm (EdDSA)", RFC 8032, Signature Algorithm (EdDSA)", RFC 8032,
DOI 10.17487/RFC8032, January 2017, DOI 10.17487/RFC8032, January 2017,
<https://www.rfc-editor.org/info/rfc8032>. <https://www.rfc-editor.org/info/rfc8032>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
12.2. Informative References 11.2. Informative References
[ED448] Hamburg, M., "Ed448-Goldilocks, a new elliptic curve", [ED448] Hamburg, M., "Ed448-Goldilocks, a new elliptic curve",
January 2015, <https://eprint.iacr.org/2015/625.pdf>. January 2015, <https://eprint.iacr.org/2015/625.pdf>.
[IANA-PKA] [IANA-SSH] IANA, "Secure Shell (SSH) Protocol Parameters",
Internet Assigned Numbers Authority (IANA), "Secure Shell <https://www.iana.org/assignments/ssh-parameters>.
(SSH) Protocol Parameters: Public Key Algorithm Names",
May 2017, <http://www.iana.org/assignments/ssh-parameters/
ssh-parameters.xhtml#ssh-parameters-19>.
[IANA-SSHFP] [IANA-SSHFP]
Internet Assigned Numbers Authority (IANA), "Secure Shell IANA, "DNS SSHFP Resource Record Parameters",
(SSH) Protocol Parameters: Public Key Algorithm Names", <https://www.iana.org/assignments/dns-sshfp-rr-
May 2017, <https://www.iana.org/assignments/dns-sshfp-rr- parameters>.
parameters/
dns-sshfp-rr-parameters.xhtml#dns-sshfp-rr-parameters-1>.
[OpenSSH-6.5] [OpenSSH-6.5]
Friedl, M., Provos, N., de Raadt, T., Steves, K., Miller, Friedl, M., Provos, N., de Raadt, T., Steves, K., Miller,
D., Tucker, D., Rice, T., and B. Lindstrom, "OpenSSH 6.5 D., Tucker, D., McIntyre, J., Rice, T., and B. Lindstrom,
release notes", January 2014, "OpenSSH 6.5 release notes", January 2014,
<http://www.openssh.com/txt/release-6.5>. <http://www.openssh.com/txt/release-6.5>.
[RFC7479] Moonesamy, S., "Using Ed25519 in SSHFP Resource Records", [RFC7479] Moonesamy, S., "Using Ed25519 in SSHFP Resource Records",
RFC 7479, DOI 10.17487/RFC7479, March 2015, RFC 7479, DOI 10.17487/RFC7479, March 2015,
<https://www.rfc-editor.org/info/rfc7479>. <https://www.rfc-editor.org/info/rfc7479>.
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.
Authors' Addresses Authors' Addresses
Ben Harris Ben Harris
2A Eachard Road 2A Eachard Road
CAMBRIDGE CB3 0HY Cambridge
UNITED KINGDOM CB3 0HY
United Kingdom
Email: bjh21@bjh21.me.uk Email: bjh21@bjh21.me.uk
Loganaden Velvindron Loganaden Velvindron
cyberstorm.mu cyberstorm.mu
88, Avenue De Plevitz 88, Avenue De Plevitz
Roches Brunes Roches Brunes
Mauritius Mauritius
Email: logan@cyberstorm.mu Email: logan@cyberstorm.mu
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