Robust multi property combiners for hash functions revisited Conference Paper

Author(s): Fischlin, Marc; Lehmann, Anja; Pietrzak, Krzysztof
Title: Robust multi property combiners for hash functions revisited
Title Series: LNCS
Abstract: A robust multi-property combiner for a set of security properties merges two hash functions such that the resulting function satisfies each of the properties which at least one of the two starting functions has. Fischlin and Lehmann (TCC 2008) recently constructed a combiner which simultaneously preserves collision-resistance, target collision-resistance, message authentication, pseudorandomness and indifferentiability from a random oracle (IRO). Their combiner produces outputs of 5n bits, where n denotes the output length of the underlying hash functions. In this paper we propose improved combiners with shorter outputs. By sacrificing the indifferentiability from random oracles we obtain a combiner which preserves all of the other aforementioned properties but with output length 2n only. This matches a lower bound for black-box combiners for collision-resistance as the only property, showing that the other properties can be achieved without penalizing the length of the hash values. We then propose a combiner which also preserves the IRO property, slightly increasing the output length to 2n + ω(logn). Finally, we show that a twist on our combiners also makes them robust for one-wayness (but at the price of a fixed input length).
Keywords: Control theory; Functions; Linguistics; Translation (languages)
Conference Title: ICALP: Automata, Languages and Programming
Volume: 5126
Issue PART 2
Conference Dates: July 7-11, 2008
Conference Location: Reykjavik, Iceland
Publisher: Springer  
Date Published: 2008-08-06
Start Page: 655
End Page: 666
Copyright Statement: © 2008 Springer-Verlag
DOI: 10.1007/978-3-540-70583-3_53
Open access: no
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