A Scheme For Digital Watermarking Based On Computer Graphic Techniques

With the developing of the Electronic Commerce, the 10th Chinese National People's Congress passed the Law on Digital Signature Scheme of the People's Republic of China.That is a real law on digital time and has been executed on April 1st in 2005. It will promote the development on Electronic Commerce.But the digital signature belongs to a kind of encryption technology, and has some inherent limitation. For too many digital files, even if the network security techniques had been mature, it still needs some methods for authentication. The digital watermarking technology can provide an invisible authentication mark for electronic files, and has increased the difficulty to counterfeit.Aiming at the security on electronic bill, the article proposes a scheme for water marking based on computer graphic technology, to defend the electronic bills from being tampered.First, select the free curve polygon as watermark information, then, encrypt the binary sequence of the polygon vertexes by Hash Function.After processing the watermark information, embed them into the wavelet field. Because the controlling points of polygon are not on the free curves, it's certainly difficult to find them only by the curves.A new algorithm has been proposed on this article, and an electronic bill example has been designed. The system can mark the fields that have been tampered. It is a novel and practical watermark technique.