Updated Security Considerations for the MD5 Message-Digest and the HMAC-MD5 Algorithms
RFC 6151
Document | Type |
RFC - Informational
(March 2011; No errata)
Was draft-turner-md5-seccon-update (individual in sec area)
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Authors | Lily Chen , Sean Turner | ||
Last updated | 2015-10-14 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 6151 (Informational) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Alexey Melnikov | ||
Send notices to | (None) |
Internet Engineering Task Force (IETF) S. Turner Request for Comments: 6151 IECA Updates: 1321, 2104 L. Chen Category: Informational NIST ISSN: 2070-1721 March 2011 Updated Security Considerations for the MD5 Message-Digest and the HMAC-MD5 Algorithms Abstract This document updates the security considerations for the MD5 message digest algorithm. It also updates the security considerations for HMAC-MD5. Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. 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). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see 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/rfc6151. Copyright Notice Copyright (c) 2011 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. Turner & Chen Informational [Page 1] RFC 6151 MD5 and HMAC-MD5 Security Considerations March 2011 1. Introduction MD5 [MD5] is a message digest algorithm that takes as input a message of arbitrary length and produces as output a 128-bit "fingerprint" or "message digest" of the input. The published attacks against MD5 show that it is not prudent to use MD5 when collision resistance is required. This document replaces the security considerations in RFC 1321 [MD5]. [HMAC] defined a mechanism for message authentication using cryptographic hash functions. Any message digest algorithm can be used, but the cryptographic strength of HMAC depends on the properties of the underlying hash function. [HMAC-MD5] defined test cases for HMAC-MD5. This document updates the security considerations in [HMAC], which [HMAC-MD5] points to for its security considerations. [HASH-Attack] summarizes the use of hashes in many protocols and discusses how attacks against a message digest algorithm's one-way and collision-free properties affect and do not affect Internet protocols. Familiarity with [HASH-Attack] is assumed. One of the uses of message digest algorithms in [HASH-Attack] was integrity protection. Where the MD5 checksum is used inline with the protocol solely to protect against errors, an MD5 checksum is still an acceptable use. Applications and protocols need to clearly state in their security considerations what security services, if any, are expected from the MD5 checksum. In fact, any application and protocol that employs MD5 for any purpose needs to clearly state the expected security services from their use of MD5. 2. Security Considerations MD5 was published in 1992 as an Informational RFC. Since that time, MD5 has been extensively studied and new cryptographic attacks have been discovered. Message digest algorithms are designed to provide collision, pre-image, and second pre-image resistance. In addition, message digest algorithms are used with a shared secret value for message authentication in HMAC, and in this context, some people may find the guidance for key lengths and algorithm strengths in [SP800-57] and [SP800-131] useful. MD5 is no longer acceptable where collision resistance is required such as digital signatures. It is not urgent to stop using MD5 in other ways, such as HMAC-MD5; however, since MD5 must not be used for digital signatures, new protocol designs should not employ HMAC-MD5. Alternatives to HMAC-MD5 include HMAC-SHA256 [HMAC] [HMAC-SHA256] and [AES-CMAC] when AES is more readily available than a hash function. Turner & Chen Informational [Page 2] RFC 6151 MD5 and HMAC-MD5 Security Considerations March 2011 2.1. Collision Resistance Pseudo-collisions for the compress function of MD5 were firstShow full document text