Security evaluation against differential and linear cryptanalyses for Feistel ciphers

Abstract

To evaluate the security against differential and linear cryptanalyses for Feistel ciphers with substitutionpermutation 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 B_d, B_l 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.

Keywords

Feistel ciphers / active s-boxes / branch number