Patent ID: 8165288

Claim:
A cryptographic processing apparatus that executes cryptographic processing to which an extended Feistel structure in which the number of data lines d is set to an integer satisfying d≧3 is applied, the apparatus comprising a data processing unit configured to modify applied round keys in encryption processing and decryption processing to execute a swapping process in the encryption processing and to execute the same swapping process in the decryption processing, wherein the swapping process sets, for the d data lines, output from a specific data line of a preceding round as input to a specific data line of a subsequent round, execute cryptographic processing in which transformation matrices of linear transformation processes are executed in F-functions of respective rounds constituting the extended Feistel structure, and perform a round key permutation process in which an applied sequence for round keys applied in respective rounds of the decryption processing is set to a sequence opposite to that of the cryptographic processing and in which round keys input to a plurality of F-functions for each of even-numbered rounds are set to have an input style different from an input style in the encryption processing.