Cryptology ePrint Archive: Report 2015/909

On the Impact of Known-Key Attacks on Hash Functions

Bart Mennink, Bart Preneel

Abstract: Hash functions are often constructed based on permutations or blockciphers, and security proofs are typically done in the ideal permutation or cipher model. However, once these random primitives are instantiated, vulnerabilities of these instantiations may nullify the security. At ASIACRYPT 2007, Knudsen and Rijmen introduced known-key security of blockciphers, which gave rise to many distinguishing attacks on existing blockcipher constructions. In this work, we analyze the impact of such attacks on primitive-based hash functions. We present and formalize the weak cipher model, which captures the case a blockcipher has a certain weakness but is perfectly random otherwise. A specific instance of this model, considering the existence of sets of B queries whose XOR equals 0 at bit-positions C, where C is an index set, covers a wide range of known-key attacks in literature. We apply this instance to the PGV compression functions, as well as to the Groestl (based on two permutations) and Shrimpton-Stam (based on three permutations) compression functions, and show that these designs do not seriously succumb to any differential known-key attack known to date.

Category / Keywords: secret-key cryptography / hash functions, known-key security, Knudsen-Rijmen, PGV, Groestl, Shrimpton-Stam, collision resistance, preimage resistance

Original Publication (with major differences): IACR-ASIACRYPT-2015

Date: received 17 Sep 2015, last revised 25 Nov 2015

Contact author: bart mennink at esat kuleuven be

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Version: 20151125:125723 (All versions of this report)

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