Information recording/reproducing device and information recording medium

An information recording/reproducing device, comprising:

• a recording medium provided with a user data recording area and an encryption key data recording area in which a time of not being able to correctly reproduce recorded data in the encryption key data recording area, is shorter than a time of not being able to correctly reproduce recorded data in the user data recording area;
• a write element of performing data recording by causing a local physical state change on the recording medium;
• a read element of performing data reproduction by reading a local physical state distribution on the recording medium;
• and
• a scanning mechanism for scanning an arbitrary position on the recording medium by the write element or the read element, wherein at the time of recording of user data, recording is performed to the user data recording area of the recording medium while encrypting the user data, and encryption key data to be used for encryption is recorded in the encryption key data recording area, and
• at the time of reproduction of the user data by a user having an authorized access right, the encryption key data is read from the encryption key data recording area, the user data encrypted at the time of recording is output while being decrypted by an encryption key once reproduced from the encryption key data recording area, and the encryption key data is overwritten on the encryption key data recording area.