Disclosed herein is an encryption and decryption communication semiconductor device comprising at least, a communication interface for performing a transfer of data according to a predetermined communication system, one or two or more encryption/decryption circuits which encrypt or decrypt input data in accordance with a predetermined algorithm, and a plurality of external interfaces for performing the input/output of data from and to external devices. The communication interface, the encryption/decryption circuits and the plurality of external interfaces are formed on one semiconductor chip. In the cryption and decryption communication semiconductor device, input data sent from any one of the plurality of external interfaces is encrypted or decrypted by at least one of the encryption/decryption circuits and is capable of being outputted to any different one of the plurality of external interfaces.