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Versions: 00

Internet Engineering Task Force                       L. Velvindron, Ed.
Internet-Draft                                                Hackers.mu
Intended status: Standards Track                          April 18, 2017
Expires: October 20, 2017


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

Abstract

   The Diffie-Hellman (DH) 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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on October 20, 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.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  2048 bits DH Group  . . . . . . . . . . . . . . . . . . . . .   2
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   2
   4.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     4.1.  Normative References  . . . . . . . . . . . . . . . . . .   3
     4.2.  Informative References  . . . . . . . . . . . . . . . . .   3
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   3

1.  Introduction

   RFC4419 [RFC4419] specifies a recommended minimum size of 1024 bits
   for k, which is the modulus length of the DH 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].

2.  2048 bits DH Group

   Recent research [LOGJAM] 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.

3.  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.



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4.  References

4.1.  Normative References

   [LOGJAM]   Adrian, D., Bhargavan, K., Durumeric, Z., Gaudry, P.,
              Green, M., Halderman, J., Heninger, N., Springall, D.,
              ThomA(C), E., Valenta, L., VanderSloot, B., Wustrow, E.,
              Zanella-BA(C)guelin, S., and P. Zimmermann, "Imperfect
              Forward Secrecy: How Diffie-Hellman Fails in Practice",
              ACM Conference on Computer and Communications Security
              (CCS) 2015, 2015, <https://weakdh.org/imperfect-forward-
              secrecy-ccs15.pdf>.

   [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>.

Author's Address

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

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
















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