Generic Indifferentiability Proofs of Hash Designs

—In this paper, we propose a formal analysis of domain extenders for hash functions in the indifferentiability framework. We define a general model for domain extenders and provide a unified proof of their security in the form of a generic reduction theorem. Our general model for domain exenders captures many iterated constructions such as domain extenders, modes of operation of symmetric cryptography such as CBCMAC or blockciphers based on Feistel networks. Its proof has been carried out using the Computational Indistinguishability Logic of Barthe et al.. The theorem can help designers of hash functions justifying the security of their constructions: they only need to bound the probability of well-defined events. Our model allows to consider many SHA-3 finalists and is instantiated on two well-known constructions, namely Chop-MD and Sponge. Finally, the indifferentiability bounds which we prove are convincing since they match previous proofs.

• Type: Journal
• Year: 2012
• Where: CSFW
• Authors: Marion Daubignard, Pierre-Alain Fouque, Yassine Lakhnech
• Keywords: CSFW 2012, Hash Functions, Reduction Theorem, Security Privacy, Symmetric Cryptography