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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force B. Harris 3 Internet-Draft 4 Updates: RFC4253 (if approved) L. Velvindron 5 Intended status: Standards Track cyberstorm.mu 6 Expires: March 12, 2020 September 9, 2019 8 Ed25519 and Ed448 public key algorithms for the Secure Shell (SSH) 9 protocol 10 draft-ietf-curdle-ssh-ed25519-ed448-11 12 Abstract 14 This document describes the use of the Ed25519 and Ed448 digital 15 signature algorithm in the Secure Shell (SSH) protocol. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at https://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on March 12, 2020. 34 Copyright Notice 36 Copyright (c) 2019 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (https://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 1. Introduction 51 Secure Shell (SSH) [RFC4251] is a secure remote-login protocol. It 52 provides for an extensible variety of public key algorithms for 53 identifying servers and users to one another. Ed25519 [RFC8032] is a 54 digital signature system. OpenSSH 6.5 [OpenSSH-6.5] introduced 55 support for using Ed25519 for server and user authentication and was 56 then followed by other SSH implementations. 58 This document describes the method implemented by OpenSSH and others, 59 and formalizes its use of the name "ssh-ed25519". Additionally, it 60 also describes the use of Ed448 and formalizes its use of the name 61 "ssh-ed448". 63 [TO BE REMOVED: Please send comments on this draft to 64 curdle@ietf.org.] 66 2. Conventions Used in This Document 68 The descriptions of key and signature formats use the notation 69 introduced in [RFC4251], Section 3 [RFC4251] and the string data type 70 from [RFC4251], Section 5 [RFC4251]. 72 2.1. Requirements Language 74 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 75 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 76 document are to be interpreted as described in RFC 2119 [RFC2119] RFC 77 8174 [RFC8174] when, and only when, they appear in all capitals, as 78 shown here. 80 3. Public Key Algorithm 82 This document describes a public key algorithm for use with SSH in 83 accordance with [RFC4253], Section 6.6 [RFC4253]. The name of the 84 algorithm is "ssh-ed25519". This algorithm only supports signing and 85 not encryption. 87 Additionally, this document describes another public key algorithm. 88 The name of the algorithm is "ssh-ed448". This algorithm only 89 supports signing and not encryption. 91 Standard implementations of SSH SHOULD implement these signature 92 algorithms. 94 4. Public Key Format 96 The "ssh-ed25519" key format has the following encoding: 98 string "ssh-ed25519" 99 string key 101 Here 'key' is the 32-octet public key described by [RFC8032], 102 Section 5.1.5 [RFC8032]. 104 The "ssh-ed448" key format has the following encoding: 106 string "ssh-ed448" 107 string key 109 Here 'key' is the 57-octet public key described by [RFC8032], 110 Section 5.2.5 [RFC8032]. 112 5. Signature Algorithm 114 Signatures are generated according to the procedure in [RFC8032], 115 Section 5.1.6 and Section 5.2.6 [RFC8032]. 117 6. Signature Format 119 The "ssh-ed25519" key format has the following encoding: 121 string "ssh-ed25519" 122 string signature 124 Here 'signature' is the 64-octet signature produced in accordance 125 with [RFC8032], Section 5.1.6 [RFC8032]. 127 The "ssh-ed448" key format has the following encoding: 129 string "ssh-ed448" 130 string signature 132 Here 'signature' is the 114-octet signature produced in accordance 133 with [RFC8032], Section 5.2.6 [RFC8032]. 135 7. Verification Algorithm 137 Ed25519 signatures are verified according to the procedure in 138 [RFC8032], Section 5.1.7 [RFC8032]. 140 Ed448 signatures are verified according to the procedure in 141 [RFC8032], Section 5.2.7 [RFC8032]. 143 8. SSHFP DNS resource records 145 Usage and generation of SSHFP DNS resource record is described in 146 [RFC4255]. The generation of SSHFP resource records for "ssh- 147 ed25519" keys is described in [RFC7479]. This section illustrates 148 the generation of SSHFP resource records for "ssh-ed448" keys and the 149 document specifies the corresponding Ed448 code point to the "SSHFP 150 RR Types for public key algorithms" IANA registry. 152 The generation of SSHFP resource records for "ssh-ed25519" keys is 153 described in [RFC7479]. 155 The generation of SSHFP resource records for "ssh-ed448" keys is 156 described as follows. 158 The encoding of Ed448 public keys is described in [ED448]. In brief, 159 an Ed448 public key is a 57-octet value representing a 455-bit 160 y-coordinate of an elliptic curve point, and a sign bit indicating 161 the the corresponding x-coordinate. 163 The SSHFP Resource Record for the Ed448 public key with SHA-256 164 fingerprint would for example be: 166 example.com. IN SSHFP TBD 2 ( a87f1b687ac0e57d2a081a2f2826723 167 34d90ed316d2b818ca9580ea384d924 01 ) 169 The 2 here indicates SHA-256 [RFC6594]. 171 9. IANA Considerations 173 This document augments the Public Key Algorithm Names in [RFC4250], 174 Section 4.6.2 [RFC4250]. 176 IANA is requested to add to the Public Key Algorithm Names registry 177 [IANA-PKA] with the following entry: 179 Public Key Algorithm Name Reference 180 ------------------------- ---------- 181 ssh-ed25519 This Draft 182 ssh-ed448 This Draft 184 IANA is requested to add the following entry to the "SSHFP RR Types 185 for public key algorithms" registry [IANA-SSHFP]: 187 +--------+-------------+------------+ 189 | Value | Description | Reference | 190 +--------+-------------+------------+ 192 | TBD | Ed448 | [this-draft] | 194 +--------+-------------+------------+ 196 We strongly suggest 6 as value. 198 [TO BE REMOVED: This registration should take place at the following 199 location: ] 202 10. Security Considerations 204 The security considerations in [RFC4251], Section 9 [RFC4251] apply 205 to all SSH implementations, including those using Ed25519 and Ed448. 207 The security considerations in [RFC8032], Section 8 [RFC8032] and 208 [RFC7479] apply to all uses of Ed25519 and Ed448 including those in 209 SSH. 211 11. Acknowledgements 213 The OpenSSH implementation of Ed25519 in SSH was written by Markus 214 Friedl. We are also grateful to Mark Baushke, Benjamin Kaduk and 215 Daniel Migault for their comments. 217 12. References 219 12.1. Normative References 221 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 222 Requirement Levels", BCP 14, RFC 2119, 223 DOI 10.17487/RFC2119, March 1997, 224 . 226 [RFC4250] Lehtinen, S. and C. Lonvick, Ed., "The Secure Shell (SSH) 227 Protocol Assigned Numbers", RFC 4250, 228 DOI 10.17487/RFC4250, January 2006, 229 . 231 [RFC4251] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH) 232 Protocol Architecture", RFC 4251, DOI 10.17487/RFC4251, 233 January 2006, . 235 [RFC4253] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH) 236 Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253, 237 January 2006, . 239 [RFC4255] Schlyter, J. and W. Griffin, "Using DNS to Securely 240 Publish Secure Shell (SSH) Key Fingerprints", RFC 4255, 241 DOI 10.17487/RFC4255, January 2006, 242 . 244 [RFC6594] Sury, O., "Use of the SHA-256 Algorithm with RSA, Digital 245 Signature Algorithm (DSA), and Elliptic Curve DSA (ECDSA) 246 in SSHFP Resource Records", RFC 6594, 247 DOI 10.17487/RFC6594, April 2012, 248 . 250 [RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital 251 Signature Algorithm (EdDSA)", RFC 8032, 252 DOI 10.17487/RFC8032, January 2017, 253 . 255 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 256 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 257 May 2017, . 259 12.2. Informative References 261 [ED448] Hamburg, M., "Ed448-Goldilocks, a new elliptic curve", 262 January 2015, . 264 [IANA-PKA] 265 Internet Assigned Numbers Authority (IANA), "Secure Shell 266 (SSH) Protocol Parameters: Public Key Algorithm Names", 267 May 2017, . 270 [IANA-SSHFP] 271 Internet Assigned Numbers Authority (IANA), "Secure Shell 272 (SSH) Protocol Parameters: Public Key Algorithm Names", 273 May 2017, . 277 [OpenSSH-6.5] 278 Friedl, M., Provos, N., de Raadt, T., Steves, K., Miller, 279 D., Tucker, D., Rice, T., and B. Lindstrom, "OpenSSH 6.5 280 release notes", January 2014, 281 . 283 [RFC7479] Moonesamy, S., "Using Ed25519 in SSHFP Resource Records", 284 RFC 7479, DOI 10.17487/RFC7479, March 2015, 285 . 287 Authors' Addresses 289 Ben Harris 290 2A Eachard Road 291 CAMBRIDGE CB3 0HY 292 UNITED KINGDOM 294 Email: bjh21@bjh21.me.uk 296 Loganaden Velvindron 297 cyberstorm.mu 298 88, Avenue De Plevitz 299 Roches Brunes 300 Mauritius 302 Email: logan@cyberstorm.mu