One document matched: draft-turner-md2-to-historic-01.txt

Differences from draft-turner-md2-to-historic-00.txt

Network Working Group                                         S. Turner 
Internet Draft                                                     IECA 
Updates: 1319, 4572 (once approved)                             L. Chen 
Intended Status: Informational                                     NIST 
Expires: January 5, 2011                                   July 5, 2010 
 
 
                                      
                          MD2 to Historic Status 
                    draft-turner-md2-to-historic-01.txt 

Abstract 

   This document recommends the retirement of MD2 and discusses the 
   reasons for doing so.  This document recommends RFC 1319 be moved to 
   Historic status.  This document also updates the IANA Hash Algorithm 
   Registry. 

Status of this Memo 

   This Internet-Draft is submitted in full conformance with the 
   provisions of BCP 78 and BCP 79.  This document may contain material 
   from IETF Documents or IETF Contributions published or made publicly 
   available before November 10, 2008. 

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Copyright Notice 

   Copyright (c) 2010 IETF Trust and the persons identified as the 
   document authors. All rights reserved. 

 
 
 
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   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 
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   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. 

1. Introduction 

   MD2 [MD2] 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.  This document recommends that MD2 be 
   retired.  Specifically, this document recommends RFC 1319 [MD2] be 
   moved to Historic status.  The reasons for taking this action are 
   discussed.  This document also updates the IANA Hash Registry. 

   [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. 

2. Rationale 

   MD2 was published in 1992 as an Informational RFC.  Since its 
   publication, MD2 has been shown to not be collision-free 
   [MD2-Analysis1] [MD2-Analysis2] [MD2-Analysis5] and shown to have 
   successful pre-image attacks [MD2-Analysis2] [MD2-Analysis3] [MD2-
   Analysis4].  In fact, RSA, in '96, suggested that MD2 should not be 
   used [RSA-AdviceOnMD2]. 

   Another consideration is that industry is independently leading the 
   charge to deprecate MD2: 

       o Many TLS implementations, OpenSSL, Network Security Services, 
        and GNUTLS, have disabled support for MD2 by default. 

       o Microsoft has also banned MD2 [MS-AdviceOnMD2]. 

3. Documents that Reference RFC 1319 

   MD2 has been specified in the following RFCs: 

   Proposed Standard (PS): 


 
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       o [RFC3279] Algorithms and Identifiers for the Internet X.509 
        Public Key Infrastructure Certificate and Certificate 
        Revocation List (CRL) Profile. 

       o [RFC4572] Connection-Oriented Media Transport over the 
        Transport Layer Security (TLS) Protocol in the Session 
        Description Protocol (SDP). 

   Informational: 

       o [RFC1983] Internet Users' Glossary. 

       o [RFC2315] PKCS #7: Cryptographic Message Syntax Version 1.5. 

       o [RFC2898] PKCS #5: Password-Based Cryptography Specification 
        Version 2.0. 

       o [RFC3447] Public-Key Cryptography Standards (PKCS) #1: RSA 
        Cryptography Specifications Version 2.1. 

   Experimental: 

       o [RFC2660] The Secure HyperText Transfer Protocol. 

   There are other RFCs that refer to MD2, but their status is either 
   Historic or Obsoleted.  References and discussions about these RFCs 
   are omitted. 

4. Impact of Moving MD2 to Historic. 

   The impact of moving MD2 to Historic on the RFCs specified in Section 
   3 is minimal, as described below.   

   Concentrating on the PS RFCs: 

       o MD2 support in TLS was dropped in TLS 1.1.  

       o MD2 support is optional in [RFC4572], and SHA-1 is specified 
        as the preferred algorithm.  

       o MD2 is included in the original PKIX certificate profile and 
        the PKIX algorithm document [RFC3279] for compatibility with 
        older applications, but its use is discouraged.  SHA-1 is 
        identified as the preferred algorithm for the Internet PKI. 




 
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   Looking at the Informational RFCs: 

       o The Internet Users' Guide [RFC1983] provided a definition for 
        Message Digest and listed MD2 as one example. 

       o PKCS#1 [RFC3447] indicates that support MD2 is only retained 
        for compatibility with existing applications.  One of the 
        motivations for updating PKCS#1 was to add support for 
        algorithms such as SHA-224, SHA-256, SHA-384, and SHA-512. 

       o PKCS#5 [RFC2898] recommends that the Password Based Encryption 
        Scheme (PBES) that uses MD2 not be used for new applications.  

       o PKCS#7 [RFC2315] was replaced by a series of standards track 
        publications, "Cryptographic Message Syntax" [RFC2630] 
        [RFC3369] [RFC5652] and "Cryptographic Message Syntax (CMS) 
        Algorithms" [RFC3370]. Support for MD2 was dropped in 
        [RFC3370].  

   RFC 2818 "HTTP Over TLS", which does not reference MD2, largely 
   supplanted implementation of [RFC2660].  [RFC2660] specified MD2 for 
   use both as a digest algorithm as a MAC algorithm [RFC2104].  Note 
   that this is the only reference to HMAC-MD2 found in the RFC 
   repository. 

5. Other Considerations 

   MD2 has also fallen out of favor because it is slower than both MD4 
   [MD4] and MD5 [MD5].  This is because MD2 was optimized for 8-bit 
   machines while MD4 and MD5 were optimized for 32-bit machines.  MD2 
   is also slower than the Secure Hash Standard (SHS) [SHS] algorithms: 
   SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512. 

6. Security Considerations 

   MD2 is differently from MD4 and MD5 in that is not a straight Merkle-
   Damgaard design. For a padded message with t blocks, it generates a 
   nonlinear checksum as its t+1 block.  The checksum is considered as 
   the final block input of MD2. 

   As confirmed in 1997 by Rogier et. al. [MD2-Analysis5], the collision 
   resistance property of MD2 highly depends on the nonlinear checksum.  
   Without the checksum, a collision can be found in 2^12 MD2 operations 
   according, while with the checksum, the best collision attack takes 
   2^63.3 operations with 2^50 memory complexity [MD2-Analysis3], which 
   is not significantly better than the birthday attack. 


 
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   Even though collision attacks on MD2 are not more powerful than the 
   birthday attack, MD2 was found not to be one way. In [MD2-Analysis4], 
   a pre-image can be found with 2^104 MD2 operations. In an improved 
   attack described in [MD2-Analysis4], a pre-image can be found in 2^73 
   MD2 operations.  Because of this "invertible" property of MD2, when 
   using MD2 in HMAC, it may leak information of the keys. 

   Obviously, the pre-image attack can be used to find a second pre-
   image.  The second pre-image attack is even more severe than 
   collision attack to digital signatures.  Therefore, MD2 must not be 
   used for digital signatures. 

   Some may find the guidance for key lengths and algorithm strengths in 
   [SP800-57] and [SP800-131] useful. 

7. Recommendation 

   Despite MD2 seeing some deployment on the Internet, this 
   specification recommends obsoleting MD2 because MD2 is not a 
   reasonable candidate for further standardization and should be 
   deprecated in favor of one or more existing hash algorithms (e.g., 
   SHA-256). 

   It takes a number of years to deploy crypto and it also takes a 
   number of years to withdraw it.  Algorithms need to be withdrawn 
   before a catastrophic break is discovered.  MD2 is clearly showing 
   signs of weakness and implementations should strongly consider 
   removing support and migrating to another hash algorithm. 

8. IANA Considerations 

   IANA is requested to update that hash registration procedures found 
   in [RFC4572] with a fourth piece of information: 

       o The intended usage of the algorithm: One of COMMON, LIMITED 
        USE or OBSOLETE. 

   IANA is further requested to add a fourth column to the IANA Hash 
   Function Textual Name Registry: Usage. 

   Finally, IANA is requested to populate the column as follows: MD2 as 
   OBSOLETE and MD5, SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512 as 
   COMMON. 





 
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9. Informative References 

   [HASH-Attack]     Hoffman, P., and B. Schneier, "Attacks on 
                     Cryptographic Hashes in Internet Protocols", RFC 
                     4270, November 2005. 

   [MD2]             Rivest, R., "The MD5 Message-Digest Algorithm", RFC 
                     1319, April 1992. 

   [MD2-Analysis1]   Rogier, N., and P. Chauvaud, "The compression 
                     function of MD2 is not collision free", Presented 
                     at Selected Areas in Cryptography '95, Carleton 
                     University, Ottawa, Canada. May 18-19, 1995. 

   [MD2-Analysis2]   Knudsen, L., and J. Mathiassen, "Preimage and 
                     Collision Attacks on MD2," FSE 2005. 

   [MD2-Analysis3]   Muller, F., "The MD2 Hash Function Is Not One-Way", 
                     ASIACRYPT, LNCS 3329, pp. 214-229, Springer, 2004. 

   [MD2-Analysis4]   Knudsen, L., Mathiassen, J., Muller, F., and 
                     Thomsen, S., "Cryptanalysis of MD2", Journal of 
                     Cryptology, 23(1):72-90, 2010. 

   [MD2-Analysis5]   Rogier, N. and P. Chauvaud, "MD2 is not secure 
                     without the checksum byte", Des. Codes Cryptogr. 
                     12(3), 245-251 (1997). 

   [MD4]             Rivest, R., "The MD4 Message-Digest Algorithm", RFC 
                     1320, April 1992. 

   [MD5]             Rivest, R., "The MD5 Message-Digest Algorithm", RFC 
                     1321, April 1992. 

   [MS-AdviceOnMD2]  Sullican, B., "Security Briefs: Cryptographic 
                     Agility", August 2009, 
                     ,http://msdn.microsoft.com/en-
                     us/magazine/dvdarchive/ee321570.aspx 

   [RFC1983]         Malkin, G., "Internet Users' Glossary", RFC 1983, 
                     August 1996. 

   [RFC2104]         Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: 
                     Keyed-Hashing for Message Authentication", RFC 
                     2104, February 1997. 

   [RFC2315]         Kaliski, B., "PKCS #7: Cryptographic Message Syntax 
                     Version 1.5," RFC 2315, March 1998. 
 
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   [RFC2630]         Housley, R., "Cryptographic Message Syntax", RFC 
                     2630, June 1999. 

   [RFC2660]         Rescorla, E., and A. Schiffman, "The Secure 
                     HyperText Transfer Protocol", RFC 2660, August 
                     1999. 

   [RFC2898]         Kaliski, B., "PKCS #5: Password-Based Cryptography 
                     Specification Version 2.0", RFC 2898, September 
                     2000. 

   [RFC3279]         Polk, W., Housley, R., and L. Bassham, "Algorithms 
                     and Identifiers for the Internet X.509 Public Key 
                     Infrastructure Certificate and Certificate 
                     Revocation List (CRL) Profile", RFC 3279, April 
                     2002. 

   [RFC3369]        Housley, R., "Cryptographic Message Syntax (CMS)", 
                    RFC 3369, August 2002. 

   [RFC3370]         Housley, R., "Cryptographic Message Syntax (CMS) 
                     Algorithms", RFC 3370, August 2002. 

   [RFC3447]         Jonsson, J. and B. Kaliski, "Public-Key 
                     Cryptography Standards (PKCS) #1: RSA Cryptography 
                     Specifications Version 2.1" RFC 3447, February 
                     2003. 

   [RFC4572]         Lennox, J., "Connection-Oriented Media Transport 
                     over the Transport Layer Security (TLS) Protocol 
                     in the Session Description Protocol (SDP)", RFC 
                     4572, July 2006. 

   [RFC5652]         Housley, R., "Cryptographic Message Syntax (CMS)", 
                     RFC 5652, August 2002. 

   [RSA-AdviceOnMD2] Robshaw, M.J.B., "On Recent Results for MD2, MD4 
                     and MD5", November 1996, 
                     ftp://ftp.rsasecurity.com/pub/pdfs/bulletn4.pdf 

   [SP800-57]        National Institute of Standards and Technology 
                     (NIST), Special Publication 800-57: Recommendation 
                     for Key Management - Part 1 (Revised), March 2007. 

   [SP800-131]       National Institute of Standards and Technology 
                     (NIST), Special Publication 800-131: DRAFT 
                     Recommendation for the Transitioning of 
                     Cryptographic Algorithms and Key Sizes, June 2010. 
 
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   [SHS]             National Institute of Standards and Technology 
                     (NIST), FIPS Publication 180-3: Secure Hash 
                     Standard, October 2008. 

Authors' Addresses 

   Sean Turner 
   IECA, Inc. 
   3057 Nutley Street, Suite 106 
   Fairfax, VA 22031 
   USA 

   EMail: turners@ieca.com 

   Lily Chen 
   National Institute of Standards and Technology 
   100 Bureau Drive, Mail Stop 8930 
   Gaithersburg, MD 20899-8930 
   USA 

   EMail: lily.chen@nist.gov 



























 
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