An input is ciphered in at least one of a sector forming circuit 13, a scrambling circuit 14, a header appendage circuit 15, an error correction encoding circuit 16, a modulation circuit 17 and a synchronization appendage circuit 18, used for processing input data for forming a recording signal. Not only key for ciphering itself in the circuits but also the information as to which of the circuits has been used for ciphering becomes the key for ciphering. This realizes ciphering difficult to decode by a simplified structure.