A recording-medium cartridge including a recording-medium and a cartridge memory. In this recording-medium cartridge, the cartridge memory holds a unique cryptographic key in the condition that the rewrite of the cryptographic key is forbidden, and is detachably attached to the recording-medium cartridge. The recording-medium holds a CRC-code, which is generated based on the cryptographic key and data to be recorded on the recording-medium, and data in the condition that the CRC-code is correlated with the data.