A recording/playback apparatus for recording or playing back content is provided. For example, a playback unit plays back a medium on which an encrypted content management unit and an encrypted unit key for encrypting the content management unit are recorded. The encrypted unit key is decrypted according to a predetermined decryption procedure. An obtaining unit obtains subsequently generated or obtained data corresponding to the content data played back by the playback unit and a subsequently generated or obtained data key. A decryption unit decrypts the subsequently generated or obtained data key obtained by the obtaining unit according to the predetermined decryption procedure for decrypting the encrypted unit key to decrypt the subsequently generated or obtained data based on the decrypted subsequently generated or obtained data key.