Patent ID: 8290148

Claim:
An encryption processing apparatus for performing common-key blockcipher processing, the encryption processing apparatus comprising: an encryption processor, comprising: an encryption processing part that is configured to perform data transformation in which a round function is iterated for a plurality of rounds, and a key scheduling part that is configured to generate round keys used to execute the round function, wherein the key scheduling part includes: a first intermediate key generating part that is configured to generate an m-bit first intermediate key by transformation of a secret key, a second intermediate key generating part that is configured to generate a plurality of different second intermediate keys by repeatedly applying an x s times multiplication over an extension field GF(2 m ), generated by an m-th order irreducible polynomial f(x) defined over GF(2), to said first intermediate key, and a round key generating part that is configured to generate a plurality of different round keys based on said second intermediate keys.