Copy protected disk

Details Copy protected disk Copy protected disk

1984-08-13

1989-04-18

Hecker, Stuart N.

Dynamic magnetic information storage or retrieval

General recording or reproducing

Recording-or erasing-prevention

360132, G11B 1504, G11B 586, G11B 1904

Patent

active

048232106

ABSTRACT:
A copy protected magnetic storage disk includes a plurality of record tracks suitable for recording information-bearing data accompanied by a clock signal having a signal strength corresponding to the signal strength of the data. At least one of the record tracks includes a recording pattern representative of a code burst derived by temporarily changing the clock signal during a recording operation. Upon playback, the recording pattern of the code burst causes a random series of playback data to be produced which are dissimilar from one playback operation to the next playback operation. To verify the status of a disk (original or a copy), the code burst is read twice. With an original disk, the playback data is dissimilar; each time a copy is read, however, the same playback data is produced.

REFERENCES:
patent: 3551608 (1970-12-01), Balink
patent: 3604104 (1961-10-01), Hembrooke
patent: 3963865 (1976-06-01), Songer
patent: 4040099 (1977-08-01), Cook
patent: 4086634 (1978-04-01), Cook
patent: 4100575 (1978-07-01), Morio et al.
patent: 4325089 (1982-04-01), Hsu
patent: 4333113 (1982-07-01), Kalinowski
patent: 4462078 (1984-07-01), Ross
patent: 4477848 (1984-10-01), McWhirter et al.
patent: 4488176 (1984-12-01), Bond
patent: 4584641 (1986-04-01), Guglielmino
patent: 4644422 (1987-02-01), Bedini
patent: 4734796 (1988-03-01), Grynberg
IBM-TDB vol. 21, No. 2, Jul. '78, Guruge Preventing Unauthorized Access to Diskette Loaded Microcode, pp. 836-837.

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