A controller to be incorporated in a storage medium device and for controlling access to the storage medium device, wherein the storage medium device includes a flash memory for storing an encrypted content encrypted by a title key and the controller comprises: a holding unit (511,512) configured to hold a controller key embedded by a mask that a controller manufacturing device uses when manufacturing the controller; a receiving unit (520,522) configured to receive an encrypted media key transmitted by a key issuance center that is authorized, wherein the encrypted media key is generated by the key issuance center through encryption of a media key with use of the controller key, and the media key is used for protecting data stored on the storage medium device; and a conversion unit (522,526) configured to perform conversion on the encrypted media key by using unique information of the controller, thereby generating an individually-converted media key; a playback device authentication unit configured (i) to perform, when the storage medium device is connected to a playback device, playback device authentication between the playback device and the storage medium device with use of the individually-converted media key, and (ii) to obtain, when the playback device and the storage medium device successfully authenticate each other, a shared key that is common to the playback device and the storage medium device; a title key decryption unit configured to decrypt, when receiving an encrypted title key from the playback device, the encrypted title key with use of the individually-converted media key; and a title key encryption unit configured to encrypt the title key decrypted by the title key decryption unit with use of the shared key; wherein the unique information of the controller is generated through applying a given one-way function to a controller unique number generated by the controller manufacturing device; the controller unique number is added to the controller through electrically burning out a part of an electronic circuit of the controller; and when manufacturing the controller, a value of the controller key is switched in lot units of a predefined number. a holding unit (511,512) configured to hold a controller key embedded by a mask that a controller manufacturing device uses when manufacturing the controller; a receiving unit (520,522) configured to receive an encrypted media key transmitted by a key issuance center that is authorized, wherein the encrypted media key is generated by the key issuance center through encryption of a media key with use of the controller key, and the media key is used for protecting data stored on the storage medium device; and a conversion unit (522,526) configured to perform conversion on the encrypted media key by using unique information of the controller, thereby generating an individually-converted media key; a playback device authentication unit configured (i) to perform, when the storage medium device is connected to a playback device, playback device authentication between the playback device and the storage medium device with use of the individually-converted media key, and (ii) to obtain, when the playback device and the storage medium device successfully authenticate each other, a shared key that is common to the playback device and the storage medium device; a title key decryption unit configured to decrypt, when receiving an encrypted title key from the playback device, the encrypted title key with use of the individually-converted media key; and a title key encryption unit configured to encrypt the title key decrypted by the title key decryption unit with use of the shared key; wherein the unique information of the controller is generated through applying a given one-way function to a controller unique number generated by the controller manufacturing device; the controller unique number is added to the controller through electrically burning out a part of an electronic circuit of the controller; and when manufacturing the controller, a value of the controller key is switched in lot units of a predefined number.