Patent ID: 8369522

Claim:
An encryption processing apparatus that performs common-key blockcipher processing, the apparatus comprising: an encryption processing part that performs data transformation processing in which a round function is repeated for a plurality of rounds; and a key scheduling part that generates round keys to be applied to executing the round function, wherein the key scheduling part includes an intermediate-key generating part that inputs a secret key to an encryption function including the round function employed by the encryption processing part and generates an intermediate key, and an intermediate-key expanding part that takes the intermediate key generated by the intermediate-key generating part as an input and generates round keys, the intermediate-key expanding part comprising: a data transformation processing part that takes the intermediate key generated by the intermediate-key generating part as an input and generates intermediate-key bijective-transformed data by performing bijective transformation, and an exclusive-OR calculating part that performs an exclusive-OR operation on one of the secret key and secret-key-transformed data generated on the basis of the secret key and on the intermediate-key bijective-transformed data generated by the data transformation processing part, wherein the intermediate-key expanding part is configured to output, as round keys, the intermediate-key bijective-transformed data, which is a result of processing performed by the data transformation processing part, and processing result data obtained by the exclusive-OR calculating part.