Cryptology ePrint Archive: Report 2007/239

Making Large Hash Functions From Small Compression Functions

William R. Speirs and Ian Molloy

Abstract: We explore the idea of creating a hash function that produces an $s$-bit digest from a compression function with an $n$-bit output, where $s > n$. % where $s\le 2^{n/2}n$.This is accomplished by truncating a hash function with a digest size of $\ell n$-bits. Our work answers the question of how large $\ell$ can be while creating a digest of $sn$-bits securely. We prove that our construction is secure with respect to preimage resistance and collision resistance for $s \le 2^{n/2}n$.

Category / Keywords: foundations / hash functions

Publication Info: Work in progress

Date: received 15 Jun 2007

Contact author: bill speirs at gmail com

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Version: 20070619:200028 (All versions of this report)

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