ENCRYPTION COMMUNICATION SYSTEM, TRANSMISSION DEVICE, RECEPTION DEVICE, ENCRYPTING/DECRYPTING METHOD AND PROGRAM THEREOF

摘要

PROBLEM TO BE SOLVED: To provide an encryption communication system and the like which reduce impossible differential characteristics and enable use of a smaller hardware while ensuring satisfactory strength.

SOLUTION: Each of encrypting means 12 and decrypting means 23 comprises: a first adder 101a in which key data acts under the exclusive OR on one of two subblock data generated by dividing input data; an S box layer 101b that performs non-linear transformation; a linear transformation layer 101c that performs linear transformation processing; and a second adder 102 that causes the other subblock data to act under the exclusive OR on an output from the linear transformation layer, each having a predetermined number of rounds. The linear transformation layer outputs output data obtained by multiplying to the input data a matrix M which is obtained by combining plural square submatrices, at least one square submatrix is an elementary matrix, and the rest is obtained as the elementary matrix exclusive-ORed with the elementary matrix the rows of which are cyclically shifted.

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