US4849836A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Copy protection for computer discs
Assignee: SOFTWARE HEAVEN Inc 6160 LUSK BOULEVARD STE C-206 SAN DIEGO CA 92121 A CORP OF CA
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Filing: 1986-07-24
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Granted: 1989-07-18
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Expires: 2006-07-24
Abstract
Abstract A copy protection system for computer discs in which a key sequence of 1101 in a copy protection section of the program is deliberately rendered ambiguous by repeatedly recording a word containing that sequence while gradually shifting the phase of the transition forming the central "1" of the sequence until the sequence becomes 1011. When this series of words is repetitively read, successive reads will be inconsistent with one another. The gradual phase shift cannot be reproduced if the disc is copied on a standard personal computer, so that the inconsistency on successive readouts will not be present in a copied disc. The program is so designed that it cannot run unless inconsistencies are detected in the copy protection section of the program. The provision of "1"s on each side of the central, variable two-bit sequence prevents spurious loss of synchronization on the copied disc which could be interpreted as an inconsistency. Alternative methods of creating synchronization-preserving ambiguities are disclosed using off-center recording of copy protection data.
Inventors
- 👤 Kevin R. Kachikian
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 22:24
CPC Classifications
G; G11; G11B; G11B20/00; G11B20/00086; G11B20/00572; G11B20/00586; G11B20/00601; G11B20/0092; G11B20/00927
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
206 words
A method of protecting a computer disc against copying, said disc containing information enabling the running of a computer program, and a data set providing an indication of copy legitimacy by causing inconsistent readouts when read repeatedly, said method comprising the steps of: (a) recording on said disc a set of data of which different portions are recorded at different phase angles; (b) causing said data set to be read repeatedly; (c) causing successive readouts of said data to be compared to one another; (d) structuring said program so that it cannot be run if said successive read-outs are consistent with one another; (e) said data set being a repetitive series of words, and said different portions being predetermined transitions within words; (f) said words of said data set including a bit sequence of two bits containing a single transition signifying a logic "1", and the phase angle of said transition being incrementally shifted in each repetition of said words within said series so as to gradually vary said bit sequence between "10" and "01"; (g) said bit sequence being flanked by a logic "1" on each side thereof to avoid loss of synchronization in the event that said bit sequence is spuriously read as "00".
Claim 2
Independent Claim
206 words
A method of protecting a computer disc against copying, said disc containing information enabling the running of a computer program, and a data set providing an indication of copy legitimacy by causing inconsistent readouts when read repeatedly, said method comprising the steps of: (a) recording on said disc a set of data of which different portions are recorded at different phase angles; (b) causing said data set to be read repeatedly; (c) causing successive readouts of said data to be compared to one another; (d) structuring said program so that it cannot be run if said successive read-outs are consistent with one another; (e) said data set being a repetitive series of words, and said different portions being predetermined transitions within words; (f) said words of said data set including a bit sequence of two bits containing a single transition signifying a logic "1", and the phase angle of said transition being incrementally shifted in each repetition of said words within said series so as to gradually vary said bit sequence between "10" and "01"; (g) said bit sequence being flanked by a logic "1" on each side thereof to avoid loss of synchronization in the event that said bit sequence is spuriously read as "00".
Claim 3
Independent Claim
121 words
A method of protecting a computer disc against copying, said disc including a data set providing an indication of copy legitimacy by causing inconsistent readouts when read repeatedly, said method comprising the steps of: (a) recording a set of data on said disc in a manner which causes it to be ambiguous upon readout; (b) causing said data set to be repeatedly read; (c) causing successive readouts of said data set to be compared to one another; (d) preventing information on said disc from being used if said successive readouts are essentially consistent with one another; and (e) said data set and said ambiguity being so structured that no readout of said ambiguous data can produce more than two successive zeros.
Claim 4
Independent Claim
121 words
A method of protecting a computer disc against copying, said disc including a data set providing an indication of copy legitimacy by causing inconsistent readouts when read repeatedly, said method comprising the steps of: (a) recording a set of data on said disc in a manner which causes it to be ambiguous upon readout; (b) causing said data set to be repeatedly read; (c) causing successive readouts of said data set to be compared to one another; (d) preventing information on said disc from being used if said successive readouts are essentially consistent with one another; and (e) said data set and said ambiguity being so structured that no readout of said ambiguous data can produce more than two successive zeros.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-07-17 | 1993-01-16 | 1993-07-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-07-17 | 1997-01-16 | 1997-07-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-07-17 | 2001-01-16 | 2001-07-18 | $7700.00 | Window Closed / Lapsed |