SPN-Hash: Improving the Provable Resistance Against Differential Collision Attacks

Abstract. Collision resistance is a fundamental property required for cryptographic hash functions. One way to ensure collision resistance is to use hash functions based on public key cryptography (PKC) which reducescollisionresistancetoahardmathematicalproblem,butsuchprimitivesareusuallyslow.Amorepracticalapproachistousesymmetric-key design techniques which lead to faster schemes, but collision resistance can only be heuristically inferred from the best probability of a single differential characteristic path. We propose a new hash function design with variable hash output sizes of 128, 256, and 512 bits, that reduces this gap. Due to its inherent Substitution-Permutation Network (SPN) structure and JH mode of operation, we are able to compute its differential collision probability using the concept of differentials. Namely, for each possible input differences, we take into account all the differential paths leading to a collision and this enables us to prove that our hash function is secure against a differential collision attack using a single input difference. None of the SHA-3 finalists could prove such a resistance. At the same time, our hash function design is secure against pre-image

The Rebound Attack and Subspace Distinguishers: Application to Whirlpool

© 2013, International Association for Cryptologic Research. We introduce the rebound attack as a variant of differential cryptanalysis on hash functions and apply it to the hash function Whirlpool, standardized by ISO/IEC. We give attacks on reduced variants of the 10-round Whirlpool hash function and compression function. Our results are collisions for 5.5 and near-collisions for 7.5 rounds on the hash function, as well as semi-free-start collisions for 7.5 and semi-free-start near-collisions for 9.5 rounds on the compression function. Additionally, we introduce the subspace problem as a generalization of near-collision resistance. Finally, we present the first distinguishers that apply to the full compression function and the full underlying block cipher W of Whirlpool.status: publishe