The operating and other procedures of a disk or recording medium application system of the type for which a network is used are simplified. Disks or recording media have auxiliary data recording areas, where different IDs for individual disk, and/or cipher keys and/or decoding keys for ciphers are recorded in advance in a factory. By using the IDs to release the soft ciphers, and using the cipher keys when sending the ciphers, and using the decoding keys when receiving the ciphers, user authorization procedures are simplified.