Internet Engineering Task Force (IETF)                         L. Camara
Internet-Draft                                          January 26, 2018
Obsoletes: 4345 (if approved)
Updates: 4253 (if approved)
Intended Status: Best Current Practice
Expires: July 30, 2018


                 Deprecating RC4 in Secure Shell (SSH)
                  draft-ietf-curdle-rc4-die-die-die-06

[[RFC-Editor: please replace the second character of my surname by
U+00E2 when publishing as RFC in the header and in all pages.
Non-ASCII characters are allowed in RFCs as per RFC 7997.]]

Abstract

   This document deprecates RC4 in Secure Shell (SSH).  Therefore, this
   document updates RFC 4253, and formally obsoletes and moves to
   Historic RFC 4345.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on July 30, 2018.

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Internet-Draft       Deprecating RC4 in Secure Shell        January 2018

Table of Contents

   1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2. Why obsolete and move to Historic RFC 4345  . . . . . . . . . .  2
   3. Updates to RFC 4253 . . . . . . . . . . . . . . . . . . . . . .  2
   4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  2
   5. Security Considerations . . . . . . . . . . . . . . . . . . . .  3
   6. Acknowlegdements  . . . . . . . . . . . . . . . . . . . . . . .  3
   7. References  . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   7.1. Normative References  . . . . . . . . . . . . . . . . . . . .  3
   7.2. Informative References  . . . . . . . . . . . . . . . . . . .  3
   8. Author's Address  . . . . . . . . . . . . . . . . . . . . . . .  3

1. Introduction

   RC4 is broken [RFC7457] and this document deprecates its use in
   Secure Shell (SSH).

   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
   BCP 14 [RFC2119, RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2. Why obsolete and move to Historic RFC 4345

   RFC 4345 defines the "arcfour-128" and "arcfour-256" modes for SSH,
   and is obsoleted and moved to Historic as RC4 is broken [RFC7457].
   The modes defined by RFC 4345 MUST NOT be used.

3. Updates to RFC 4253

   RFC 4253 is updated to prohibit arcfour's use in SSH.

   The last sentence of the paragraph on RC4 (called "arcfour"
   in [RFC4253]) in Section 6.3 of [RFC4253] should read: "Arcfour (also
   known as RC4) is broken [RFC7457] and therefore it MUST NOT be used."

   An informative reference to RFC 7457 is to be added to [RFC4253].

4. IANA Considerations

   IANA may need to take action as the status for RC4 and 3DES
   algorithms for Secure Shell (SSH) is changed by this document
   (see Section 3, that updates [RFC4253]).





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Internet-Draft       Deprecating RC4 in Secure Shell        January 2018

5. Security Considerations

   This document only prohibits the use of RC4 in SSH, and introduces no
   new security considerations.

6. Acknowledgements

   Thanks to the numerous authors which have shown the weaknesses of
   RC4 throughout the years, and to the several people which have
   commented on the CURDLE mailing list about this document.

7. References

7.1. Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in
              RFC 2119 Key Words", BCP 14, RFC 8174, May 2017.

7.2. Informative References

   [RFC4253]  Ylonen, T., and C. Lonvick, Ed., "The Secure Shell (SSH)
              Transport Layer Protocol", RFC 4253, January 2006.

   [RFC7457]  Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing
              Known Attacks on Transport Layer Security (TLS) and
              Datagram TLS (DTLS)", RFC 7457, February 2015.

   [[RFC-Editor: please replace the 'i' in my name by U+00ED and the
   first 'a' in the surname by U+00E2, as non-ASCII characters are
   allowed as per RFC 7997]]

8. Author's Address

   Luis Camara

   EMail: <luis.camara@live.com.pt>













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