In a method for preventing unauthorized use of a recording medium having a user accessible area and a user inaccessible area, first information is read from the user inaccessible area of the recording medium. The first information is compared with second information concerning a true recording medium...http://www.google.com.au/patents/US5982886?utm_source=gb-gplus-sharePatent US5982886 - Unauthorized use preventing method for optical disks, optical disk having unauthorized use prevention function, and optical disk apparatus
