Encryption method, encryption apparatus, decryption method, and decryption apparatus

摘要

The subkey data generating unit 101 has two different subkey key generation processes. When encrypting a (T*n) plaintext block (where T denotes a predetermined cycle and n is a positive integer), sixteen sets of subkey data are generated. In all other cases, two sets of subkey data are generated. The encrypting unit 100 encrypts the plaintext using the generated sixteen or two sets of subkey data.