Patent ID: 7979915

Claim:
A playback device that reads encrypted data from a recording medium and controls an execution of decryption processing to decrypt the read encrypted data, wherein the recording medium includes a first area located at a first physical position and a second area located at a second physical position different from the first physical position, wherein decryption information is prerecorded in the first area of the recording medium before the encrypted data is recorded by a recording device, the decryption information being used to perform the decryption processing to decrypt the encrypted data, wherein the encrypted data is generated by encrypting, using the decryption information, data targeted for recording, wherein certain information is recorded in the second area of the recording medium, and wherein the playback device comprises: a determination unit including a processor operable to determine whether the decryption information recorded in the first area and the certain information recorded in the second area are identical; and a control unit operable, when the determination unit determines that the decryption information recorded in the first area and the certain information recorded in the second area are not identical, to execute the decryption processing to decrypt the encrypted data using the decryption information read from the first area.