In an encryption-decryption apparatus, a transmitting apparatus encrypts input
data to output encrypted data. A network transmits the encrypted data. A receiving
apparatus takes as input the encrypted data transmitted through the network, and
decrypts the data to send output data. A variable configuration processing circuit
encrypts the input data. A ROM outputs circuit data serving as a secret key to
the variable configuration processing circuit. Another variable configuration processing
circuit decrypts the encrypted data. Another ROM outputs circuit data serving as
a secret key to the variable configuration processing circuit. This enables a change
in hardware according update of an encryption-decryption algorithm, and more rapid
processing of the encryption-decryption operation.
