Watermarking electronic text documents
US8014557B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 17, 2004 |
| Grant date | Sep 6, 2011 |
| Priority date | — |
| Expiry date | Jan 15, 2027 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N2201/3284
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A text watermarking method embeds an auxiliary message in an original electronic text document to form a watermarked text document. The method applies a spreading function to message symbols to spread the symbols over a carrier, which forms a modulated carrier. It maps elements of the modulated carrier to corresponding inter-word spaces in the electronic text document, and applies an embedding function to modify the corresponding inter-word spaces according to elements of the modulated carrier signal such that the modified inter-word spaces hide the modulated carrier signal in the watermarked text document. The message symbols are automatically decodable from the watermarked document without the original electronic text document. A compatible decoder extracts the auxiliary message from a printed or electronic watermarked text document. The decoder automatically measures inter-word spaces in the watermarked text document. It estimates elements of a modulated carrier signal embedded in the inter-word spaces to form an estimated modulated carrier signal, and applies a de-spreading function to the estimated modulated carrier signal to extract message symbols.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.