A data storage unit may store an encrypted medium device key Enc (Kcu, Kmd_i), and a medium device key certificate (Certmedia). A controller further includes: an information recording unit configured to store a controller key (Kc) and first controller identification information (IDcu). A key generation unit executes a one-way function calculation based on the controller key and the first controller identification information to generate a controller unique key (Kcu). An identification information generating unit executes a one-way function calculation based on the controller key and the first controller identification information to generate second controller identification information (IDcntr). A key encryption unit encrypts the medium device key (Kmd_i) by the controller unique key (Kcu) to generate encrypted medium device key Enc (Kcu, Kmd_i). A key exchange unit executes an authentication key exchange process with a host device using the medium device key (Kmd_i) and the medium device key certificate (Certmedia).