A recording device configured to store content data in an encrypted manner, the recording device comprises a memory unit which stores various data, and a controller which controls the memory unit. The controller possesses a controller key and unique identification information, and is configured to generate a controller-unique key unique for each controller in accordance with the controller key and the identification information. The memory unit stores an MKB generated by encrypting a medium key with a device key set that is a collection of a plurality of device keys, an encrypted device key set generated by encrypting the device key set with the controller-unique key, and a device-key-set index which uniquely identifies the device key set. The controller comprises a decryption unit which obtains a device key set by decrypting the encrypted device key set with the controller-unique key, an ID generating unit which generates a medium ID from the identification information and the device-key-set index, and an authentication unit which executes an authentication process with an exterior in accordance with the device key set, the medium ID and the MKB.