## CryptoDB

### Paper: How to Build a Hash Function from any Collision-Resistant Function

Authors: Thomas Ristenpart Thomas Shrimpton URL: http://eprint.iacr.org/2008/189 Search ePrint Search Google Recent collision-finding attacks against hash functions such as MD5 and SHA-1 motivate the use of provably collision-resistant (CR) functions in their place. Finding a collision in a provably CR function implies the ability to solve some hard problem (e.g., factoring). Unfortunately, existing provably CR functions make poor replacements for hash functions as they fail to deliver behaviors demanded by practical use. In particular, they are easily distinguished from a random oracle. We initiate an investigation into building hhash functions from provably CR functions. As a method for achieving this, we present the Mix-Compress-Mix (MCM) construction; it envelopes any provably CR function H (with suitable regularity properties) between two injective mixing'' stages. The MCM construction simultaneously enjoys (1) provable collision-resistance in the standard model, and (2) indifferentiability from a monolithic random oracle when the mixing stages themselves are indifferentiable from a random oracle that observes injectivity. We instantiate our new design approach by specifying a blockcipher-based construction that appropriately realizes the mixing stages.
##### BibTeX
@misc{eprint-2008-17866,
title={How to Build a Hash Function from any Collision-Resistant Function},
booktitle={IACR Eprint archive},
keywords={Hash functions, random oracle, collision-resistance, pseudorandom oracles, indifferentiability},
url={http://eprint.iacr.org/2008/189},
note={A preliminary version appeared at Asiacrypt 2007. tristenp@cs.ucsd.edu 13995 received 26 Apr 2008, last revised 26 Apr 2008},
author={Thomas Ristenpart and Thomas Shrimpton},
year=2008
}