| 摘要 |
PROBLEM TO BE SOLVED: To effectively protect profit of a copyright holder by limiting the state to access authentication information having identification information at least peculiar to the device based on the authentication information recorded according to minute variations on an information recording surface as compared with pits or marks forming pit trains or mark trains. SOLUTION: A laser control circuit 5 drivers an optical pickup 4B, and intermittently increases a light quantity of a laser beam. By increasing this light quantity, authentication information PW containing key information KY necessary for the access of an optical disk 2 and a device number SD being identification information, is recorded on an optical disk 2 by adjusting a reflection factor to vary about 1% in a small area as compared with a pit of the optical disk 2. The optical pickup 4A, an AD circuit 29, and an authentication information decoding circuit 30 reproduces the authentication information PW recorded on the optical disk, and detects authentication information US. A CPU unit 9 limits the access to the optical disk 2 based on the key information KY and the device number SD of the authentication information US. |
