Secure optically readable memory usable in connection with a limited number of machines

摘要

Digital information stored on a CD-ROM is accessible by use of a password, which is readable initially on the CD-ROM and which subsequently becomes at least partially unreadable due to exposure of the CD-ROM to the radiation used to read the CD-ROM. A user machine which read the password before the password became at least partially unreadable may subsequently use it to access encrypted information on the CD-ROM, while a user machine which has not read the password before it became at least partially unreadable will be unable subsequently to read the password, and hence unable to access encrypted information on the CD-ROM.