Method and system for protecting digital data from unauthorized copying
US6539475B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 18, 1998 |
| Grant date | Mar 25, 2003 |
| Priority date | — |
| Expiry date | Dec 18, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N2005/91364
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Data is protected from unauthorized copying by rescrambling an unauthorized version of the data, but descrambling an authorized version of the data. This is done using a trigger signal. One property of the trigger signal is that it is preserved through signal transformations, such as one or more of compression, decompression, analog to digital conversion, and digital to analog conversion. As a result of this property the trigger signal can be detected in either scrambled or descrambled data. The trigger signal is embedded into the data to form watermarked data. The watermarked data is passed through a descrambler, where the trigger signal, if present, is extracted. A descrambling key and a descrambling algorithm are applied to the watermarked data if the trigger signal is present, but not applied to the watermarked data if the trigger signal is not present.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.