In order to facilitate the management of the hardware key of a library apparatus employing the LTO system, a write function of a noncontact memory (CM: cartridge memory) contained in an LTO tape cartridge is implemented in a medium carrying mechanism part of the library apparatus, and during an insertion to a tape drive, the IDs unique to a library control part and to the medium carrying mechanism part are recorded in the non-contact memory and utilized as the hardware key of an encrypting apparatus. The hardware key written once is overwritten (erased) during an ejection, thereby preventing leakage of key information.