Linear frameworks for block ciphers

In this paper we generalize the structure of the cipher:; Shark, Square. BK SQ, Crypton and Rijndael. We show that the linear components play an essent ial role in the effect of the nonlinear S-boxes in providing resistance aga inst differential and linear cryptanalysis and provide upper bounds for the probability of differential characteristics and the correlation of linear approximations for the general structure. We show how good linear component s can be constructed efficiently from Maximum-Distance Separable codes. The presented block cipher structure can make optimal use of a wide range of p rocessor word lengths and its parallelism allows very fast dedicated hardwa re implementations. Ciphers with variable block length can be constructed b y varying certain parameters in the presented structure.