Cryptology ePrint Archive: Report 2006/187

On the Security of HMAC and NMAC Based on HAVAL, MD4, MD5, SHA-0 and SHA-1

Jongsung Kim and Alex Biryukov and Bart Preneel and Seokhie Hong

Abstract: HMAC is a widely used message authentication code and a pseudorandom function generator based on cryptographic hash functions such as MD5 and SHA-1. It has been standardized by ANSI, IETF, ISO and NIST. HMAC is proved to be secure as long as the compression function of the underlying hash function is a pseudorandom function. In this paper we devise two new distinguishers of the structure of HMAC, called {\em differential} and {\em rectangle distinguishers}, and use them to discuss the security of HMAC based on HAVAL, MD4, MD5, SHA-0 and SHA-1. We show how to distinguish HMAC with reduced or full versions of these cryptographic hash functions from a random function or from HMAC with a random function. We also show how to use our differential distinguisher to devise a forgery attack on HMAC. Our distinguishing and forgery attacks can also be mounted on NMAC based on HAVAL, MD4, MD5, SHA-0 and SHA-1. Furthermore, we show that our differential and rectangle distinguishers can lead to second-preimage attacks on HMAC and NMAC.

Category / Keywords: secret-key cryptography / Message Authentication Codes, HMAC, NMAC, distinguishing and forgery attacks

Publication Info: A shorted version of the paper will be published in the proceedings of SCN 2006.

Date: received 12 Jun 2006

Contact author: Kim Jongsung at esat kuleuven be

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Version: 20060619:211101 (All versions of this report)

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