Method And Device For Securing Block Ciphers Against Template Attacks

Abstract

A method for securing a block cipher F, encrypted with a working key K0, against template attacks is provided. A working permutation F(K0) fixed by the block cipher F and the working key K0, and a number N of dummy permutations G(K1), . . . , G(Kn) are provided. The N dummy permutations G(K1), . . . , G(Kn) are fixed by N dummy keys K1, . . . , Kn and the block cipher F or the inverse F−1 of the block cipher F. The working permutation F(K0) and the N dummy permutations G(K1), . . . , (G(Kn) are chained to form a chain H in such a way that the chain H and the working permutation F(K0) produce an identical image (H=F(K0)). A block cipher F, in which a fixed key K0 is used, is protected against template attacks as a result. A computer program product and a device for securing a block cipher F against template attacks are also proposed.

Dependencies are inferred from the claim text.