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Versions: 00 01 02 03 04 05 draft-ietf-krb-wg-des-die-die-die

Network Working Group                               L. Hornquist Astrand
Internet-Draft                                                Apple, Inc
Updates: 1964, 1510, 3961, 4120,                           July 10, 2010
4121 (if approved)
Intended status: Standards Track
Expires: January 11, 2011


                   Deprecate DES support for Kerberos
                      draft-lha-des-die-die-die-05

Abstract

   A long long time ago Data Encryption Standard (DES) was standardized.
   Some 30 years later (2003) is was withdrawn as a standard by National
   Institute of Standards and Technology (NIST), today 6 years later,
   its time for DES to finally die.  By 2008 it was possible to brute
   force DES keys in 6.4 days using less than USD 10k worth of hardware.
   So by 2008 DES had passed its sell-by date.  This document updates
   RFC1964, RFC4120, and RFC4121 to deprecate the use of DES in
   Kerberos.  Because the version of Kerberos specified in RFC1510 only
   supports DES and has been replaced by RFC4120, RFC1510 is
   reclassified as historic.

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 January 11, 2011.

Copyright Notice

   Copyright (c) 2010 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



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   (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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.












































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1.  Requirements Notation

   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].














































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2.  Background

   Kerberos 5 was defined in [RFC1510] and updated in [RFC4120], the
   Kerberos crypto system is defined by [RFC3961] and includes support
   for DES encryption types.  This document updates [RFC1964],
   [RFC4120], and [RFC4121] to deprecate the use of DES in Kerberos.

   Because the version of Kerberos specified in [RFC1510] only supports
   DES and has been replaced by [RFC4120], [RFC1510] is reclassified as
   historic.

   DES was withdrawn in [DES-Transition-Plan] by National Institute of
   Standards and Technology (NIST).  IETF have also published its the
   position in [RFC4772], which in the recommendation summery is made
   very clear: "don't use DES".

   In Kerberos Generic Security Services Application Programming
   Interface (GSS-API) mechanism [RFC1964] and the updated version
   [RFC4121] the following checksum and encryption mechanism is defined:
   three SGN ALG: 0000 - DES MAC MD5, 0100 - MD2.5 0200 - DES MAC and
   one SEAL ALG 0000 - DES.  With newer encryption types for Kerberos
   defined in [RFC4121], Microsofts ARCFOUR4-HMAC based GSS-API mech,
   and MITs DES3 , there is no need to support the old DES based SGN/
   SEAL types.



























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3.  Recommendations

   This document removes the RECOMMENDED types from [RFC4120]:

      Encryption: DES-CBC-MD5(3)

      Checksums: DES-MD5 (8, RSA-MD5-DES from [RFC3961]).

   Kerberos implementation and deployments SHOULD NOT implement the
   single DES encryption types: DES-CBC-CRC(1), DES-CBC-MD4(2), DES-CBC-
   MD5(3).

   Kerberos implementation and deployments SHOULD NOT implement the
   checksum type: CRC32(1), RSA-MD4(2), RSA-MD4-DES(3), DES-MAC(4), DES-
   MAC-K(5), RSA-MD4-MAC-K(6), DES-MD5(7), RSA-MD5-DES(8).

   Note that RSA-MD5 might be with non-DES encryption types, for
   example, when doing a TGS-REQ with a ARCFOUR-HMAC-MD5 some client
   uses RSA-MD5 for the checksum that is stored inside the encrypted
   part of the authenticator.  This use of RSA-MD5 should probably be
   considered safe, so the Kerberos implementation should make sure this
   usage is not disabled when used with legacy system that can't handle
   newer checksum types.

   Kerberos GSS mechanism implementation and deployments SHOULD NOT
   implement the SGN ALG: DES MAC MD5(0000), MD2.5(0100), DES MAC(0200)
   (updates [RFC1964]).

   Kerberos GSS mechanism implementation and deployments SHOULD NOT
   implement the SEAL ALG: DES(0000) (updates [RFC1964]).

   The effect of the two last sentences is that this document deprecates
   section 1.2 in [RFC1964].


















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4.  Acknowledgements

   Jeffrey Hutzelman, Simon Josefsson, Mattias Amnefelt and Leif
   Johansson have read the document and provided suggestions for
   improvements.  Sam hartman proposed moving [RFC1510] to historic.














































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5.  Security Considerations

   Removing support for single DES improves security since DES is
   considered to be insecure.















































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6.  IANA Considerations

   There are no IANA Considerations for this document
















































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7.  References

7.1.  Normative References

   [RFC1964]  Linn, J., "The Kerberos Version 5 GSS-API Mechanism",
              RFC 1964, June 1996.

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

   [RFC3961]  Raeburn, K., "Encryption and Checksum Specifications for
              Kerberos 5", RFC 3961, February 2005.

   [RFC4120]  Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The
              Kerberos Network Authentication Service (V5)", RFC 4120,
              July 2005.

   [RFC4121]  Zhu, L., Jaganathan, K., and S. Hartman, "The Kerberos
              Version 5 Generic Security Service Application Program
              Interface (GSS-API) Mechanism: Version 2", RFC 4121,
              July 2005.

7.2.  Informative References

   [DES-Transition-Plan]
              National Institute of Standards and Technology, "DES
              Transition Plan - Federal Register / Vol. 70, No. 96",
              May 2006.

   [RFC1510]  Kohl, J. and B. Neuman, "The Kerberos Network
              Authentication Service (V5)", RFC 1510, September 1993.

   [RFC4772]  Kelly, S., "Security Implications of Using the Data
              Encryption Standard (DES)", RFC 4772, December 2006.

















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Author's Address

   Love Hornquist Astrand
   Apple, Inc
   Cupertino
   USA

   Email: lha@apple.com











































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