Patent ID: 6938162

Claim:
An optical disk of recording type on which data is recordable, wherein said optical disk has a sector structure comprising a plurality of sectors, wherein each of the plurality of sectors includes a sector header area and a main data area for recording encrypted data therein, wherein the sector header area includes a decipher key information area for recording therein at least one decipher key which is required for decrypting the encrypted data, wherein a size of the decipher key information area is smaller than a size of each decipher key, wherein the respective decipher keys which are required for decrypting the encrypted data are recorded in a decipher key table having a plurality of decipher keys, wherein indexes for indicating recorded positions of the decipher keys which are required for decrypting the encrypted data within the decipher key table are recorded in the decipher key information areas of the plurality of sectors, respectively, and wherein decipher key status areas for recording decipher key statuses of the respective decipher key areas of said decipher key table are recorded as information for representing a recorded status of the decipher key table.