Security evaluation against differential and linear cryptanalyses for Feistel ciphers

Abstract

To evaluate the security against differential and linear cryptanalyses for Feistel ciphers with substitution-permutation network (SPN) round function, we consider the lower bounds of the number of differential and linear active s-boxes, which provides the upper bounds of the maximum differential and linear characteristic probabilities of Feistel ciphers. Concretely, using differential and linear branch numbers Bd, Bl of P transformation within the round function, we give new lower bounds of the number of active s-boxes in any consecutive rounds of Feistel ciphers, respectively. Furthermore, we show that our results are better than others by comparing these results.