More Modular Exponential (MODP) Diffie-Hellman (DH) Key Exchange (KEX) Groups for Secure Shell (SSH)

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Last updated 2017-05-10
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Internet Engineering Task Force                               M. Baushke
Internet-Draft                                    Juniper Networks, Inc.
Updates: 4250, 4253 (if approved)                            May 8, 2017
Intended status: Standards Track
Expires: November 9, 2017

 More Modular Exponential (MODP) Diffie-Hellman (DH) Key Exchange (KEX)
                     Groups for Secure Shell (SSH)


   This document defines added Modular Exponential (MODP) Groups for the
   Secure Shell (SSH) protocol using SHA-2 hashes.  This document
   updates RFC 4250.  This document updates RFC 4253.

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 November 9, 2017.

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Internet-Draft       More MODP DH KEX Groups for SSH            May 2017

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

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

   It is intended that these new MODP groups with SHA-2 based hashes
   update the [RFC4253] section 6.4 and [RFC4250] section 4.10

   [TO BE REMOVED: Please send comments on this draft to]

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

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