How to Use Merkle-Damgård -- On the Security Relations between Signature Schemes and Their Inner Hash Functions

  • Authors:
  • Emmanuel Bresson;Benoît Chevallier-Mames;Christophe Clavier;Aline Gouget;Pascal Paillier;Thomas Peyrin

  • Affiliations:
  • DCSSI, Paris Cedex 07, France 75700;DCSSI, Paris Cedex 07, France 75700;Gemalto, Meudon, France 92190;Gemalto, La Ciotat, France 13705;Gemalto, La Ciotat, France 13705;Orange Labs, Issy-les-Moulineaux, France 92794

  • Venue:
  • ProvSec '08 Proceedings of the 2nd International Conference on Provable Security
  • Year:
  • 2008

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Abstract

This paper reports a thorough standard-model investigation on how attacks on hash functions impact the security of hash-and-sign signature schemes. We identify two important properties that appear to be crucial in analyzing the nature of security relations between signature schemes and their inner hash functions: primitiveness and injectivity. We then investigate the security relations in the general case of hash-and-sign signatures and in the particular case of first-hash-then-sign signatures, showing a gap of security guarantees between the two paradigms. We subsequently apply our results on two operating modes to construct a hash function family from a hash function based on the well-known Merkle-Damgård construction (such as MD5 and SHA-1). For completeness, we give concrete attack workloads for attacking operating modes used in practical implementations of signature schemes.