Deprecate DES, RC4-HMAC-EXP, and Other Weak Cryptographic Algorithms in Kerberos
RFC 6649
Document | Type |
RFC - Best Current Practice
(July 2012; No errata)
Obsoletes RFC 1510
Also known as BCP 179
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Last updated | 2015-10-14 | ||
Replaces | draft-lha-des-die-die-die | ||
Stream | IETF | ||
Formats | plain text pdf html bibtex | ||
Reviews | |||
Stream | WG state | Submitted to IESG for Publication | |
Document shepherd | Sam Hartman | ||
IESG | IESG state | RFC 6649 (Best Current Practice) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Stephen Farrell | ||
IESG note | Sam Hartman (hartmans-ietf@mit.edu) is the document shepherd. | ||
Send notices to | (None) |
Internet Engineering Task Force (IETF) L. Hornquist Astrand Request for Comments: 6649 Apple, Inc. BCP: 179 T. Yu Obsoletes: 1510 MIT Kerberos Consortium Updates: 1964, 4120, 4121, 4757 July 2012 Category: Best Current Practice ISSN: 2070-1721 Deprecate DES, RC4-HMAC-EXP, and Other Weak Cryptographic Algorithms in Kerberos Abstract The Kerberos 5 network authentication protocol, originally specified in RFC 1510, can use the Data Encryption Standard (DES) for encryption. Almost 30 years after first publishing DES, the National Institute of Standards and Technology (NIST) finally withdrew the standard in 2005, reflecting a long-established consensus that DES is insufficiently secure. By 2008, commercial hardware costing less than USD 15,000 could break DES keys in less than a day on average. DES is long past its sell-by date. Accordingly, this document updates RFC 1964, RFC 4120, RFC 4121, and RFC 4757 to deprecate the use of DES, RC4-HMAC-EXP, and other weak cryptographic algorithms in Kerberos. Because RFC 1510 (obsoleted by RFC 4120) supports only DES, this document recommends the reclassification of RFC 1510 as Historic. Status of This Memo This memo documents an Internet Best Current Practice. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on BCPs is available in Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6649. Hornquist Astrand & Yu Best Current Practice [Page 1] RFC 6649 Deprecate DES in Kerberos July 2012 Copyright Notice Copyright (c) 2012 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 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. Hornquist Astrand & Yu Best Current Practice [Page 2] RFC 6649 Deprecate DES in Kerberos July 2012 1. Introduction The original specification of the Kerberos 5 network authentication protocol [RFC1510] supports only the Data Encryption Standard (DES) for encryption. For many years, the cryptographic community has regarded DES as providing inadequate security, mostly because of its small key size. Accordingly, this document recommends the reclassification of [RFC1510] (obsoleted by [RFC4120]) as Historic and updates current Kerberos-related specifications [RFC1964], [RFC4120], and [RFC4121] to deprecate the use of DES and other weak cryptographic algorithms in Kerberos, including some unkeyed checksums and hashes, along with the weak 56-bit "export strength" RC4 variant encryption type of [RFC4757]. 2. 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]. 3. Affected Specifications The original IETF specification of Kerberos 5 [RFC1510] only supports DES for encryption. [RFC4120] obsoletes [RFC1510] and updates the Kerberos specification to include additional cryptographic algorithms, but still permits the use of DES. [RFC3961] describes the Kerberos cryptographic system and includes support for DES encryption types, but it does not specify requirement levels for them. The specification of the Kerberos Generic Security Services Application Programming Interface (GSS-API) mechanism [RFC1964] and its updated version [RFC4121] define checksum and encryption mechanisms based on DES. With the existence of newer encryption types for Kerberos GSS-API defined in [RFC4121], Microsoft's RC4-HMAC-based GSS-API mechanism, and MIT's DES3 (which is not published as an RFC), there is no need to support the old DES-based integrity (SGN) and confidentiality (SEAL) types. [RFC4757] describes the RC4-HMAC encryption types used by MicrosoftShow full document text