Internet Engineering Task Force                       L. Velvindron, Ed.
Internet-Draft                                         Hackers Mauritius
Intended status: Standards Track                          March 10, 2017
Expires: September 11, 2017


         Increase minimum recommended modulus size to 2048 bits
                 draft-lvelvindron-dh-group-exchange-00

Abstract

   The Diffie-Hellman Group Exchange for the Secure Shell (SSH)
   Transport layer Protocol specifies that servers and clients should
   support groups with a modulus length of k bits, where the recommended
   minumum value is 1024 bits.  Recent security research has shown that
   a minimum value of 1024 bits is insufficient against state-sponsored
   actors.  As such, this document formally updates RFC 4419 [RFC4419]
   such that the minimum recommended value for k is 2048 bits and the
   group size is 2048 bits at minimum.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 11, 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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



Velvindron             Expires September 11, 2017               [Page 1]

Internet-Draft      Recommended minimum modulus size          March 2017


   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  2048 bits Diffie-Hellman Group  . . . . . . . . . . . . . . .   2
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   4.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     4.1.  Normative References  . . . . . . . . . . . . . . . . . .   3
     4.2.  Informative References  . . . . . . . . . . . . . . . . .   3
     4.3.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   3

.  Introduction

   RFC4419 [RFC4419] specifies a recommended minimum size of 1024 for k,
   which is the modulus length of the Diffie-Hellman Group.  It also
   suggests that in all cases, the size of the group needs be at least
   1024 bits.  This document updates RFC 4419 [RFC4419] so that the
   minimum recommended size be 2048 bits

1.1.  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 RFC 2119 [RFC2119].

.  2048 bits Diffie-Hellman Group

   Recent research [LOGJAM]  [1] strongly suggests that DH groups that
   are 1024 bits can be broken by state actors, and possibly an
   organization with enough computing resources.  The authors show how
   they are able to break 768 bits DH group and extrapolate the attack
   to 1024 bits DH groups.  In their analysis, they show that breaking
   1024 bits can be done with enough computing resources.  This document
   updates section 3 Paragraph 9 : Servers and clients SHOULD support
   groups with a modulus length of k bits where 2048 <= k <= 8192.  The
   recommended minimum values for min and max are 2048 and 8192,
   respectively.  This document also updates Section 3 Paragraph 11: In
   all cases, ths size of the group SHOULD be at least 2048 bits.








Velvindron             Expires September 11, 2017               [Page 2]

Internet-Draft      Recommended minimum modulus size          March 2017


.  Security Considerations

   This document discusses security issues of DH groups that are 1024
   bits in size, and formally updates the minimum size of DH groups to
   be 2048 bits.

.  References

4.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

4.2.  Informative References

   [RFC4419]  Friedl, M., Provos, N., and W. Simpson, "Diffie-Hellman
              Group Exchange for the Secure Shell (SSH) Transport Layer
              Protocol", RFC 4419, DOI 10.17487/RFC4419, March 2006,
              <http://www.rfc-editor.org/info/rfc4419>.

4.3.  URIs

   [] https://weakdh.org/imperfect-forward-secrecy-ccs15.pdf

Author's Address

   Loganaden Velvindron (editor)
   Hackers Mauritius
   88, Avenue De Plevitz
   Roches Brunes
   MU

   Phone: +230 59762817
   Email: logan@hackers.mu















Velvindron             Expires September 11, 2017               [Page 3]