An MPEG board 6 issues the key data generated by the board to a DVD drive 4. The DVD drive 4 generates enciphering key data on the basis of the key data, enciphers the provided data read from a DVD 2 on the basis of the key data, and sends it to the MPEG board 6. The MPEG board 6 deciphers the enciphered provided data using the key data generated by the board.