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Abstract. In this paper, we propose a new Cellular Automata (CA) based scalable parameterized hash function family named CASH. The construction of CASH is inspired by sponge function and the internal round transformation employs linear CA. For the first time, we have managed to merge the classical add-round-constant and subsequent diffusion layers. The primitive function of CASH family is proved to be secure against the state-of-the-art attacks. All the designs are implemented on Xilinx Virtex-6 FPGAs and compared with the best reported results in literature. The results show that CASH outperforms the SHA-3 finalists with respect to throughput and throughput/area.

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In this work we show the existence of special sets of inputs for which the sum of the images under SHA3 exhibits a symmetric property. We develop an analytical framework which accounts for the existence of these sets. The framework constitutes identification of a generic property of iterated SPN based functions pertaining to the round-constant addition and combining it with the notion of m−fold vectorial derivatives for differentiation over specially selected subspaces. Based on this we propose a new distinguisher called SymSum for the SHA3 family which penetrates up to 9 rounds and outperforms the ZeroSum distinguisher by a factor of four. Interestingly, the current work is the first analysis of SHA3/Keccak that relies on round-constants but is independent of their Hamming-weights.

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