A Novel Digital Watermarking Algorithm Based On SVD And Spread Spectrum

The information exchange based on computer networks has provided great convenience to the usage and spreading of the digital multimedia products. However, the digital products are illegally copied and tampered very easily, which makes its information security and copyright protection a factual problem to be solved urgently. Taking use of the redundant data and randomicity of the digital products, the digital watermarking technology embeds the unperceivable but recognizable secret information—watermark containing the copyright information into the digital products, which can protect the copyright and integrality of the digital products. The digital watermarking technology has been used widely and become the research focus, which becomes an effective method to solve the digital information security problem, especially the copyright protection of digital products.In the thesis, the basic principle and the research status worldwide of the digital watermarking technology are introduced briefly. And the principles of spread spectrum technique and singular value decomposition (SVD) are presented, on which a novel digital watermarking algorithm based on singular value decomposition and spread spectrum technique is proposed. In this algorithm, the watermark information is gotten scrambling before being embedded into the cover image. The scrambling position is taken as the key to generate a sequence of spread spectrum code that will spread the spectrum of the watermark scrambled. This pretreatment will improve the secrecy of the whole transmission system. After undergoing the pretreatment. the watermark is embedded into the SVD domain of the cover image. So, the signal embedded is randomized even if the original watermark image is meaningful, which will great improve the secrecy of the whole system. Compared with the conventional digital watermarking schemes, this algorithm, focusing on the protection of the meaningful watermark, has better performance on secrecy and robustness. Because the algorithm adopts the integrated technologies like SVD and spread spectrum, the secrecy of the watermark is enhanced, and the robustness of the watermarked imageis very well, which attains the aim of copyright protection. At last, the experimental results of the algorithm are given, as well as the results of the rectangle images and color images. The capacity of the digital watermarking is discussed too.A great deal of experimental results are presented, proving that the digital watermark generated by the algorithm is unperceivable and shows great robustness to the common image processing like low-pass filtering, median filtering, Wiener filtering, nosing, cropping, rotation and JPEG loss compression, etc. Furthermore, the algorithm is adaptive to all sorts of meaningful watermarks.