VERSCHLÜSSELUNGSGERÄT

摘要

In a secret-key cryptographic device, there are cascade-connected a plurality of round processing parts and the round processing part of each i-th round is supplied with input data Li and Ri, nonlinearly transforms the input data Ri in a nonlinear function part on the basis of extended key, then provides the exclusive OR between the nonlinearly transformed output and the input data Li as data Ri+1 for input into the next round and outputs the input data Ri as data Li+1 for input into the next round. The nonlinear function part of each round comprises: a key-dependent linear transformation part which performs a key-dependent linear transformation of the input Ri; a splitting part which splits the linearly transformed output to four pieces of data in0, in1, in2 and in3; first nonlinear transformation parts which nonlinearly transform the four split pieces of data and output nonlinearly transformed data mid00, mid01, mid02 and mid03, respectively; a key-dependent linear transformation part which associates these transformed outputs with each other and, at the same time, linearly transforms them based on extended key to output data mid10, mid11, mid12 and mid13; second nonlinear transformation parts which nonlinearly transform these transformed outputs, respectively, and output data out0, out1, out2 and out3; and a combining part which combines these transformed outputs into output data Y.