04785361 is referenced by 111 patents and cites 2 patents.

Authorized disks made in accordance with the invention are physically distinguishable from the blank disks which would be used for making unauthorized copies. A security check procedure is included in the initializing routine that is recorded on the authorized disk and that is executed prior to the reading out of any of the protected data. The security check procedure involves a test to determine whether the disk on which it has been recorded has or does not have the physical fingerprint that is the hallmark of an authorized disk. If the fingerprint is absent, the security check procedure prevents the protected material from being read out. Thus, unauthorized copies are useless because the protected data cannot be read out of them.

Title
Method and apparatus for frustrating the unauthorized copying of recorded data
Application Number
439907
Publication Number
4785361
Application Date
December 16, 1986
Publication Date
November 15, 1988
Inventor
W Krag Brotby
Pasadena
CA, US
Agent
Blakely Sokoloff Taylor & Zafman
Assignee
Vault Corporation
CA, US
IPC
G11B 15/04
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