The subkey data generating unit 101 has two different subkey key generation
processes. When encrypting a (T*n)th plaintex 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 plaintex using the generated sixteen or two sets of
subkey data.
