RFC 6149

MD2 to Historic Status

📅 published March 2011, from ietf

MD2 to Historic Status 💅

Okay bestie, here's the header tea 🫖✨ This is RFC 6149, an Informational doc, which means it's published for info and is NOT a Standards Track spec 🙈 It was written by S. Turner (IECA) and L. Chen (NIST) in March 2011. It's the official retirement notice for MD2 🪦, and it obsoletes RFC 1319, the original MD2 spec. The ISSN is 2070-1721 🎀

Abstract

okay so this doc officially retires MD2 and explains why we're doing it 💀 It also moves RFC 1319 over to Historic status 🦋

Status of This Memo

Not a Standards Track spec, just informational vibes 💜

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 🌸

Info about the current status of this doc, any errata, and how to give feedback can be found at http://www.rfc-editor.org/info/rfc6149 ✨

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, since 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 📜

1. Introduction ✨

So MD2 [MD2] is a message digest algorithm 🍓 It takes in a message of arbitrary length and spits out a 128-bit "fingerprint" or "message digest" of the input. This document retires MD2. Specifically, it moves RFC 1319 [MD2] to Historic status, and the reasons for doing that get discussed 🙈

[HASH-Attack] summarizes how hashes get used in lots of protocols, and it discusses how attacks against a message digest algorithm's one-way and collision-free properties do and don't affect Internet protocols. Familiarity with [HASH-Attack] is assumed, bestie 💅

2. Rationale

MD2 was published in 1992 as an Informational RFC 🕰️ Since then, it's been shown to not be collision-free [ROCH1995] [KNMA2005] [ROCH1997] 💀 Successful collision attacks on properly implemented MD2 aren't that damaging, though, albeit they still count as a problem 🙃 Successful pre-image and second pre-image attacks against MD2 have also been shown [KNMA2005] [MULL2004] [KMM2010] 😭

3. Documents that Reference RFC 1319

Use of MD2 has been specified in the following RFCs 📚

Proposed Standard (PS):

  • [RFC3279] Algorithms and Identifiers for the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile. 🎀
  • [RFC4572] Connection-Oriented Media Transport over the Transport Layer Security (TLS) Protocol in the Session Description Protocol (SDP). 🦋

Informational:

  • [RFC1983] Internet Users' Glossary. 🌈
  • [RFC2315] PKCS #7: Cryptographic Message Syntax Version 1.5. 🧚
  • [RFC2898] PKCS #5: Password-Based Cryptography Specification Version 2.0. 🌸
  • [RFC3447] Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1. ✨

Experimental:

  • [RFC2660] The Secure HyperText Transfer Protocol. 🔥

There are other RFCs that refer to MD2, but they've either been moved to Historic status or obsoleted by a later RFC, so their references and discussions are omitted 🙈 The exceptions are:

  • [RFC2313] PKCS #1: RSA Encryption Version 1.5. 💜
  • [RFC2437] PKCS #1: RSA Cryptography Specifications Version 2.0. 💅

4. Impact on Moving MD2 to Historic

The impact of moving MD2 to Historic on the RFCs specified in Section 3 is minimal, as described below. Honestly, it's giving low drama 🫶

Regarding PS RFCs:

  • MD2 support in TLS was dropped in TLS 1.1. 🔥
  • MD2 support is optional in [RFC4572], and SHA-1 is specified as the preferred algorithm. 🌈
  • 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. 🎀

Regarding Informational RFCs:

  • The Internet Users' Guide [RFC1983] provided a definition for Message Digest and listed MD2 as one example. 📚
  • PKCS#1 v1.5 [RFC2313] stated that there are no known attacks against MD2. PKCS#1 v2.0 [RFC2437] updated this stance to indicate that MD2 should only be supported for backward compatibility, and to mention the attacks in [ROCH1995]. PKCS#1 [RFC3447] indicates that support of MD2 is only retained for compatibility with existing applications. 🙃
  • PKCS#5 [RFC2898] recommends that the Password-Based Encryption Scheme (PBES) that uses MD2 not be used for new applications. 🧚
  • 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 and as a MAC (Message Authentication Code) algorithm [RFC2104]. Note that this is the only reference to HMAC-MD2 found in the RFC repository. 👀

Part 1 of 2 ✨ Part 2 is coming next, bestie 💖

9. Informative References 🧾

okay bestie, time for the receipts 🧾💅 these are all the sources the doc points to, and yes the list is LONG, we love a well-cited spec 🍓

  • [HASH-Attack] Hoffman, P. and B. Schneier, "Attacks on Cryptographic Hashes in Internet Protocols", RFC 4270, November 2005.
  • [KMM2010] Knudsen, L., Mathiassen, J., Muller, F., and Thomsen, S., "Cryptanalysis of MD2", Journal of Cryptology, 23(1):72-90, 2010.
  • [KNMA2005] Knudsen, L., and J. Mathiassen, "Preimage and Collision Attacks on MD2", FSE 2005.
  • [MD2] Kaliski, B., "The MD2 Message-Digest Algorithm", RFC 1319, April 1992.
  • [MD4] Rivest, R., "The MD4 Message-Digest Algorithm", RFC 1320, April 1992.
  • [MD5] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April 1992.
  • [MULL2004] Muller, F., "The MD2 Hash Function Is Not One-Way", ASIACRYPT, LNCS 3329, pp. 214-229, Springer, 2004.
  • [RFC1983] Malkin, G., Ed., "Internet Users' Glossary", FYI 18, RFC 1983, August 1996.
  • [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-Hashing for Message Authentication", RFC 2104, February 1997.
  • [RFC2313] Kaliski, B., "PKCS #1: RSA Encryption Version 1.5", RFC 2313, March 1998.
  • [RFC2315] Kaliski, B., "PKCS #7: Cryptographic Message Syntax Version 1.5", RFC 2315, March 1998.
  • [RFC2437] Kaliski, B. and J. Staddon, "PKCS #1: RSA Cryptography Specifications Version 2.0", RFC 2437, October 1998.
  • [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] Bassham, L., Polk, W., and R. Housley, "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)", STD 70, RFC 5652, September 2009.
  • [ROCH1995] 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.
  • [ROCH1997] Rogier, N. and P. Chauvaud, "MD2 is not secure without the checksum byte", Des. Codes Cryptogr. 12(3), 245-251 (1997).
  • [SHS] National Institute of Standards and Technology (NIST), FIPS Publication 180-3: Secure Hash Standard, October 2008.
  • [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.

Authors' Addresses 💌

the authors, with their contact info, verbatim 🫶

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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