Device and method for encrypting and decrypting a block of data

摘要

Method to encrypt or decrypt blocks of data X to Y, based on a main key R, using several serially connected modules, each module using a sub-key RA derived from the main key R and comprising the steps of: inputting at least two initial values X0L and X0R, and mixing them to form a mixed value X1, obtaining a value X2 by mixing a first part RAH of the sub-key RA with the value X1, obtaining a value X3 by applying the value X2 to a substitution layer comprising at least one substitution box (sbox), obtaining a value X4 by using a diffusion box of multi-permutation type based on the value X3, obtaining a value X5 by mixing a second part RAL of the sub-key RA with the value X4, obtaining the value X6 by applying to the value X5 a substitution layer, obtaining a value X7 by mixing a first part RAH of the sub-key RA with the value X6, mixing the value X7 with the initial at least two values X0L and X0R to obtain the at least two values X8L and X8R, X8L and X8R representing the output value X8 of the module. This method uses at least two modules, and applies to at least one of the values X8L or X8R an orthomorphism function before feeding them to the next module.