ENCRYPTION DEVICE, ENCRYPTION METHOD, AND PROGRAM

摘要

Resistance to the denial-of-difference attack and saturation attack of k-series generalized Feistel-type common key block cipher is improved. An encryption device comprises: a nonlinear conversion unit which takes odd-series data (Bi) (i: an odd number) of k-series data {B1, ???, Bk} (k is an even number of 6 or more) as intermediate data (Wi) and which takes the exclusive-OR between the data obtained by converting the odd-series data (Bi)on the basis of an F function and even-series data (Bi+1) as data (Wi+1); and a transposition unit which includes at least one of the transpositions from Wm (m: an odd number) into Bn (n: an even number), which satisfies the relation of n?m+2 mod k, and includes at least one of the transpositions from Wn into Bm,which satisfies the relation of m?n+2 mod k, and which performs transposition so as not to transpose Wm+1 into Bn-1 when the Wm is transposed into the Bn.