< draft-turner-md5-seccon-update-01.txt   draft-turner-md5-seccon-update-02.txt >
Network Working Group S. Turner Network Working Group S. Turner
Internet Draft IECA Internet Draft IECA
Updates: 1321, 2202 (once approved) L. Chen Updates: 1321, 2202 (once approved) L. Chen
Intended Status: Informational NIST Intended Status: Informational NIST
Expires: January 8, 2011 July 8, 2010 Expires: January 12, 2011 July 12, 2010
Updated Security Considerations for the Updated Security Considerations for the
MD5 Message-Digest Algorithm and HMAC-MD5 MD5 Message-Digest and the HMAC-MD5 Algorithms
draft-turner-md5-seccon-update-01.txt draft-turner-md5-seccon-update-02.txt
Abstract Abstract
This document updates the security considerations for the MD5 message This document updates the security considerations for the MD5 message
digest algorithm. It also updates the security considerations for digest algorithm. It also updates the security considerations for
HMAC-MD5. HMAC-MD5.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on January 8, 2011. This Internet-Draft will expire on January 12, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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MD5 has been studied extensively. What follows are recent attacks MD5 has been studied extensively. What follows are recent attacks
against MD5's collisions, pre-image, and second pre-image resistance. against MD5's collisions, pre-image, and second pre-image resistance.
Additionally, attacks against MD5 used in message authentication with Additionally, attacks against MD5 used in message authentication with
a shared secret (i.e., HMAC-MD5) are discussed. a shared secret (i.e., HMAC-MD5) are discussed.
Some may find the guidance for key lengths and algorithm strengths in Some may find the guidance for key lengths and algorithm strengths in
[SP800-57] and [SP800-131] useful. [SP800-57] and [SP800-131] useful.
2.1. Collision Resistance 2.1. Collision Resistance
The first paper that demonstrates actual collisions of MD5 was Psuedo-collisions for the compress function of MD5 were first
published in 2004 [WFLY2004]. The detailed attack techniques for MD5 described in 1993 [denBBO1993]. In 1996, [DOB1995] demonstrated a
were published at EUROCRYPT 2005 [WAYU2005]. Since then, a lot of collision pair for the MD5 compression function with a chosen initial
research results have been published to improve collision attacks on value. The first paper that demonstrated two collision pairs for
MD5. The attacks presented in [KLIM2006] can find MD5 collision in regular MD5 was published in 2004 [WFLY2004]. The detailed attack
about one minute on a standard notebook PC (Intel Pentium, 1.6 GHz.). techniques for MD5 were published at EUROCRYPT 2005 [WAYU2005]. Since
In [STEV2007], he claim that it takes 10 seconds or less on a 2.6Ghz then, a lot of research results have been published to improve
Pentium4 to find collisions. In collision attacks on MD5. The attacks presented in [KLIM2006] can
find MD5 collision in about one minute on a standard notebook PC
(Intel Pentium, 1.6 GHz.). In [STEV2007], he claim that it takes 10
seconds or less on a 2.6Ghz Pentium4 to find collisions. In
[STEV2007][SLdeW2007][SSALMOdeW2009][SLdeW2009], the collision [STEV2007][SLdeW2007][SSALMOdeW2009][SLdeW2009], the collision
attacks on MD5 were successfully applied to X.509 certificates. attacks on MD5 were successfully applied to X.509 certificates.
Notice that the collision attack on MD5 can also be applied to Notice that the collision attack on MD5 can also be applied to
password based challenge-and-response authentication protocols such password based challenge-and-response authentication protocols such
as APOP protocol used in post office authentication as presented in as APOP protocol used in post office authentication as presented in
[LEUR2007]. [LEUR2007].
In fact, more delicate attacks on MD5 to improve the speed of finding In fact, more delicate attacks on MD5 to improve the speed of finding
collisions have published recently. However, the aforementioned collisions have published recently. However, the aforementioned
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The attacks on HMAC-MD5 do not seem to indicate a practical The attacks on HMAC-MD5 do not seem to indicate a practical
vulnerability when used as a message authentication code. Considering vulnerability when used as a message authentication code. Considering
that the distinguishing-H attack is different from distinguishing-R that the distinguishing-H attack is different from distinguishing-R
attack, which distinguishes an HMAC from a random function, the attack, which distinguishes an HMAC from a random function, the
practical impact on HMAC usage as a PRF such as in a key derivation practical impact on HMAC usage as a PRF such as in a key derivation
function is not well understood. function is not well understood.
Therefore, it may not be urgent to remove HMAC-MD5 from the existing Therefore, it may not be urgent to remove HMAC-MD5 from the existing
protocols. However, since MD5 must not be used for digital protocols. However, since MD5 must not be used for digital
signatures, for a new protocol design, a ciphersuite with HMAC-MD5 signatures, for a new protocol design, a ciphersuite with HMAC-MD5
should not be included. should not be included. Options include HMAC-SHA256 [HMAC][HMAC-
SHA256] and [AES-CMAC] when AES is more readily available than a hash
function.
3. IANA Considerations 3. IANA Considerations
None. None.
4. Normative References 4. Acknowledgements
Obviously, we have to thank all the cryptographers who produced the
results we refer to in this document. We'd also like to thank Martin
Rex and Benne de Weger for their comments.
5. Normative References
[AES-CMAC] Song, J., Poovendran, R., Lee., J., and T. Iwata,
"The AES-CMAC Algorithm", RFC 4493, June 2006.
[COYI2006] S. Contini, Y.L. Yin. Forgery and partial key- [COYI2006] S. Contini, Y.L. Yin. Forgery and partial key-
recovery attacks on HMAC and NMAC using hash recovery attacks on HMAC and NMAC using hash
collisions. ASIACRYPT 2006. LNCS 4284, Springer, collisions. ASIACRYPT 2006. LNCS 4284, Springer,
2006. 2006.
[denBBO1993] den Boer, B. and A. Bosselaers, "Collisions for the
compression function of MD5", Eurocrypt 1993.
[DOB1995] Dobbertin, H., "Cryptanalysis of MD5 Compress",
Eurocrypt 1996.
[FLN2007] Fouque, P.-A., Leurent, G., Nguyen, P.Q.: Full key- [FLN2007] Fouque, P.-A., Leurent, G., Nguyen, P.Q.: Full key-
recovery attacks on HMAC/NMAC-MD4 and NMAC-MD5. recovery attacks on HMAC/NMAC-MD4 and NMAC-MD5.
CRYPTO 2007. LNCS, 4622, Springer, 2007. CRYPTO 2007. LNCS, 4622, Springer, 2007.
[HASH-Attack] Hoffman, P., and B. Schneier, "Attacks on [HASH-Attack] Hoffman, P., and B. Schneier, "Attacks on
Cryptographic Hashes in Internet Protocols", RFC Cryptographic Hashes in Internet Protocols", RFC
4270, November 2005. 4270, November 2005.
[HMAC] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: [HMAC] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC:
Keyed-Hashing for Message Authentication", RFC Keyed-Hashing for Message Authentication", RFC
2104, February 1997. 2104, February 1997.
[HMAC-MD5] Cheng, P., and R. Glenn, "Test Cases for HMAC-MD5 [HMAC-MD5] Cheng, P., and R. Glenn, "Test Cases for HMAC-MD5
and HMAC-SHA-1", RC 2201, September 1997. and HMAC-SHA-1", RC 2201, September 1997.
[HMAC-SHA256] Nystrom, M., "Identifiers and Test Vectors for
HMAC-SHA-224, HMAC-SHA-256, HMAC-SHA-384, and
HMAC-SHA-512", RFC 4231, December 2005.
[KLIM2006] V. Klima. Tunnels in Hash Functions: MD5 Collisions [KLIM2006] V. Klima. Tunnels in Hash Functions: MD5 Collisions
within a Minute. Cryptology ePrint Archive, Report within a Minute. Cryptology ePrint Archive, Report
2006/105 (2006), http://eprint.iacr.org/2006/105. 2006/105 (2006), http://eprint.iacr.org/2006/105.
[LEUR2007] G. Leurent, Message freedom in MD4 and MD5 [LEUR2007] G. Leurent, Message freedom in MD4 and MD5
collisions: Application to APOP. Proceedings of collisions: Application to APOP. Proceedings of
FSE 2007. Lecture Notes in Computer Science 4715. FSE 2007. Lecture Notes in Computer Science 4715.
Springer 2007. Springer 2007.
[MD5] Rivest, R., "The MD5 Message-Digest Algorithm", RFC [MD5] Rivest, R., "The MD5 Message-Digest Algorithm", RFC
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