A block cipher method eliminates the overhead associated with key
scheduling, decreases the required time for encryption or decryption, and
increases the total throughput. A key scheduling circuit (12) for
generating round key data from key data for the encryption or the
decryption and a bank memory (13) for storing the round key data
generated by the key scheduling circuit (12) at a predetermined bank of
the bank memory are provided. An encrypting/decrypting circuit (11) is
provided for encrypting plaintext data or decrypting ciphertext data upon
receipt of the round key data stored in the bank and a block of the
plaintext data or the ciphertext data one by one. The output of the
encryption or the decryption is retrieved from the encrypting/decrypting
circuit (11).