## CryptoDB

### Paper: Foundations of Non-Malleable Hash and One-Way Functions

Authors: Alexandra Boldyreva David Cash Marc Fischlin Bogdan Warinschi URL: http://eprint.iacr.org/2009/065 Search ePrint Search Google Non-malleability is an interesting and useful property which ensures that a cryptographic protocol preserves the independence of the underlying values: given for example an encryption Enc(m) of some unknown message m, it should be hard to transform this ciphertext into some encryption Enc(m*) of a related message m*. This notion has been studied extensively for primitives like encryption, commitments and zero-knowledge. Non-malleability of one-way functions and hash functions has surfaced as a crucial property in several recent results, but it has not undergone a comprehensive treatment so far. In this paper we initiate the study of such non-malleable functions. We start with the design of an appropriate security definition. We then show that non-malleability for hash and one-way functions can be achieved, via a theoretical construction that uses perfectly one-way hash functions and simulation-sound non-interactive zero-knowledge proofs of knowledge (NIZKPoK). We also discuss the complexity of non-malleable hash and one-way functions. Specifically, we give a black-box based separation of non-malleable functions from one-way permutations (which our construction bypasses due to the 'non-black-box' NIZKPoK). We exemplify the usefulness of our definition in cryptographic applications by showing that non-malleability is necessary and sufficient to securely replace one of the two random oracles in the IND-CCA encryption scheme by Bellare and Rogaway, and to improve the security of client-server puzzles.
##### BibTeX
@misc{eprint-2009-18247,
title={Foundations of Non-Malleable Hash and One-Way Functions},
booktitle={IACR Eprint archive},
keywords={foundations / Non-malleability, hash function, perfect one-wayness.},
url={http://eprint.iacr.org/2009/065},
note={ marc.fischlin@gmail.com 14284 received 9 Feb 2009},
author={Alexandra Boldyreva and David Cash and Marc Fischlin and Bogdan Warinschi},
year=2009
}