Key Exchange (KEX) Method Updates and Recommendations for Secure Shell (SSH)
draft-ietf-curdle-ssh-kex-sha2-07

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Last updated 2017-03-27
Replaces draft-baushke-ssh-dh-group-sha2
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Internet Engineering Task Force                               M. Baushke
Internet-Draft                                    Juniper Networks, Inc.
Updates: 4250, 4253 (if approved)                         March 27, 2017
Intended status: Standards Track
Expires: September 28, 2017

 Key Exchange (KEX) Method Updates and Recommendations for Secure Shell
                                 (SSH)
                   draft-ietf-curdle-ssh-kex-sha2-07

Abstract

   This document is intended to update the recommended set of key
   exchange methods for use in the Secure Shell (SSH) protocol to meet
   evolving needs for stronger security.  This RFC updates [RFC4253]
   MUST algorithms.  This RFC also notes that the [IANASSH] has replaced
   [RFC4250] as the primary reference document for SSH Protocol Assigned
   Numbers.

   This document adds recommendations for adoption of Key Exchange
   Methods which MUST, SHOULD+, SHOULD, SHOULD-, MAY, SHOULD NOT, and
   MUST NOT be implemented.  New key exchange methods will use the SHA-2
   family of hashes and are drawn from these from
   [I-D.ietf-curdle-ssh-curves] and new-modp from the
   [I-D.ietf-curdle-ssh-modp-dh-sha2] and gss-keyex [NEWGSSAPI].

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
   Task Force (IETF).  Note that other groups may also distribute
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 28, 2017.

Baushke                Expires September 28, 2017               [Page 1]
Internet-Draft KEX Method Updates/Recommendations for SSH     March 2017

Copyright Notice

   Copyright (c) 2017 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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Table of Contents

   1.  Overview and Rationale  . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Key Exchange Methods  . . . . . . . . . . . . . . . . . . . .   3
     3.1.  curve25519-sha256 . . . . . . . . . . . . . . . . . . . .   4
     3.2.  diffie-hellman-group-exchange-sha1  . . . . . . . . . . .   4
     3.3.  diffie-hellman-group1-sha1  . . . . . . . . . . . . . . .   4
     3.4.  diffie-hellman-group14-sha1 . . . . . . . . . . . . . . .   4
     3.5.  diffie-hellman-group14-sha256 . . . . . . . . . . . . . .   4
     3.6.  diffie-hellman-group16-sha512 . . . . . . . . . . . . . .   4
     3.7.  ecdh-sha2-nistp256  . . . . . . . . . . . . . . . . . . .   5
     3.8.  ecdh-sha2-nistp384  . . . . . . . . . . . . . . . . . . .   5
     3.9.  gss-gex-sha1-*  . . . . . . . . . . . . . . . . . . . . .   5
     3.10. gss-group1-sha1-* . . . . . . . . . . . . . . . . . . . .   5
     3.11. gss-group14-sha1-*  . . . . . . . . . . . . . . . . . . .   5
     3.12. gss-group14-sha256-*  . . . . . . . . . . . . . . . . . .   6
     3.13. gss-group16-sha512-*  . . . . . . . . . . . . . . . . . .   6
     3.14. rsa1024-sha1  . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Summary Guidance for Key Exchange Method Names  . . . . . . .   6
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Overview and Rationale

   Secure Shell (SSH) is a common protocol for secure communication on
   the Internet.  In [RFC4253], SSH originally defined two Key Exchange
   Method Names that MUST be implemented.  Over time, what was once
   considered secure, is no longer considered secure.  The purpose of
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