Network Working Group L. Hornquist Astrand Internet-Draft Apple, Inc Updates: 3961, 4120 August 2, 2009 (if approved) Intended status: Standards Track Expires: February 3, 2010 Deprecate DES support for Kerberos draft-lha-des-die-die-die-01 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on February 3, 2010. Copyright Notice Copyright (c) 2009 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Hornquist Astrand Expires February 3, 2010 [Page 1] Internet-Draft Deprecate DES support for Kerberos August 2009 Abstract A long long time ago DES was standardized. Some 30 years later (2003) is was withdrawn as a standard by NIST, today 6 years later, its time for DES to finally die.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. Use in Kerberos should therefore stop. Hornquist Astrand Expires February 3, 2010 [Page 2] Internet-Draft Deprecate DES support for Kerberos August 2009 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]. Hornquist Astrand Expires February 3, 2010 [Page 3] Internet-Draft Deprecate DES support for Kerberos August 2009 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 move all of the DES encryption and related checksum types to historic. DES was withdrawn in [DES-Transition-Plan] by NIST. IETF have also published its the position in [RFC4772], which in the recommendation summery is made very clear: "don't use DES". Hornquist Astrand Expires February 3, 2010 [Page 4] Internet-Draft Deprecate DES support for Kerberos August 2009 3. Recommendations This document removes the mandatory-to-implement types from [RFC4120]: Encryption: DES-CBC-MD5 This document removes the mandatory-to-implement types from [RFC4120] when used in conjunction with DES-CBC-MD5: Checksums: DES-MD5 Kerberos implementation and deployments SHOULD NOT implement the single DES encryption types: DES-CBC-MD5, DES-CBC-MD4, DES-CBC-CRC. Kerberos implementation and deployments SHOULD NOT implement the checksum type: CRC, RSA-MD4, RSA-MD4-DES, RSA-MAC, RSA-MAC-K, RSA- MD5, RSA-MD5-DES. 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. Hornquist Astrand Expires February 3, 2010 [Page 5] Internet-Draft Deprecate DES support for Kerberos August 2009 4. Acknowledgements Jeffery Hutzelman, Simon Josefsson, Mattias Amnefelt and Leif Johansson have read the document and provided suggestions for improvements. Hornquist Astrand Expires February 3, 2010 [Page 6] Internet-Draft Deprecate DES support for Kerberos August 2009 5. Security Considerations Removing support for single DES improves security since DES is considered to be insecure by most parties. Hornquist Astrand Expires February 3, 2010 [Page 7] Internet-Draft Deprecate DES support for Kerberos August 2009 6. IANA Considerations There are no IANA Considerations for this document Hornquist Astrand Expires February 3, 2010 [Page 8] Internet-Draft Deprecate DES support for Kerberos August 2009 7. References 7.1. Normative References [RFC1510] Kohl, J. and B. Neuman, "The Kerberos Network Authentication Service (V5)", RFC 1510, September 1993. [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. 7.2. Informative References [DES-Transition-Plan] National Institute of Standards and Technology, "DES Transition Plan - Federal Register / Vol. 70, No. 96", May 2006. [RFC4772] Kelly, S., "Security Implications of Using the Data Encryption Standard (DES)", RFC 4772, December 2006. Hornquist Astrand Expires February 3, 2010 [Page 9] Internet-Draft Deprecate DES support for Kerberos August 2009 Author's Address Love Hornquist Astrand Apple, Inc Cupertino USA Email: lha@apple.com Hornquist Astrand Expires February 3, 2010 [Page 10]