More Modular Exponential (MODP) Diffie-Hellman (DH) Key Exchange (KEX) Groups for Secure Shell (SSH)
draft-ietf-curdle-ssh-modp-dh-sha2-03

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Last updated 2017-03-27
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Internet Engineering Task Force                               M. Baushke
Internet-Draft                                    Juniper Networks, Inc.
Updates: 4253, 4432 (if approved)                         March 27, 2017
Intended status: Standards Track
Expires: September 28, 2017

 More Modular Exponential (MODP) Diffie-Hellman (DH) Key Exchange (KEX)
                     Groups for Secure Shell (SSH)
                 draft-ietf-curdle-ssh-modp-dh-sha2-03

Abstract

   This document defines added Modular Exponential (MODP) Groups for the
   Secure Shell (SSH) protocol using SHA-2 hashes.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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

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1.  Overview and Rationale

   Secure Shell (SSH) is a common protocol for secure communication on
   the Internet.  Due to recent security concerns with SHA-1 [RFC6194]
   and with MODP groups with less than 2048 bits [NIST-SP-800-131Ar1]
   implementer and users request support for larger Diffie Hellman (DH)
   MODP group sizes with data integrity verification using the SHA-2
   family of secure hash algorithms as well as MODP groups providing
   more security.

   The United States Information Assurance Directorate at the National
   Security Agency has published a FAQ [MFQ-U-OO-815099-15] suggesting
   both: a) DH groups using less than 3072-bits, and b) the use of SHA-2
   based hashes less than SHA2-384, are no longer sufficient for
   transport of Top Secret information.  For this reason, the new MODP
   groups are being introduced starting with the MODP 3072-bit group 15
   are all using SHA2-512 as the hash algorithm.

   The DH 2048-bit MODP group 14 is already present in most SSH
   implementations and most implementations already have a SHA2-256
   implementation, so diffie-hellman-group14-sha256 is provided as an
   easy to implement and faster to use key exchange for small embedded
   applications.

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

2.  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 [RFC2119].

3.  Key Exchange Algorithms

   This memo adopts the style and conventions of [RFC4253] in specifying
   how the use of new data key exchange is indicated in SSH.

   The following new key exchange algorithms are defined:

   Key Exchange Method Name
   diffie-hellman-group14-sha256
   diffie-hellman-group15-sha512
   diffie-hellman-group16-sha512
   diffie-hellman-group17-sha512
   diffie-hellman-group18-sha512

                                 Figure 1

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   The SHA-2 family of secure hash algorithms are defined in
   [FIPS-180-4].

   The method of key exchange used for the name "diffie-hellman-
   group14-sha256" is the same as that for "diffie-hellman-group14-sha1"
   except that the SHA2-256 hash algorithm is used.

   The group15 through group18 names are the same as those specified in
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