Study On Robust Digital Watermark

Digital watermark is some labels or signatures which are embedded into digital multimedia, then carries out the functions such as information hiding , storing, copyright safeguarding by tracking the use of the digital multimedia by detecting the watermarks. At present, watermark technology becomes a kind of effective means to multimedia copyright authentication and its integrity safeguarding.In this thesis, we firstly summarize the research background, applications of digital watermark and the state of the art, then we mainly focus our research on the robustness of the digital watermark-watermark recovery at the present of stochastic noise and geometric attacks in a blind watermarking system. The valuable research fruits are as follows:We introduce a transform domain watermarking algorithm based on Block-SVD. It has very good robustness. This algorithm can come over bugs of the traditional SVD that more time is spent in computing the SVs. In the method, first, digital watermark is encrypted with chaotic mapping,then the host image is divided into several blocks, the extract the SVD in the each block, and embed the watermark, finally gait the image which contains watermark. Extensive experiments show that the new method is very robust against image distortion.In the second part of the thesis, our researcher is on the basis of feature point and images invariant moment to geometrical, a watermarking scheme for digital image that can resist to geometrical attacks is proposed. In the process of embedding, we embed watermark around the feature point which is extracted from the normalized image. In blind watermark detection process, we also extract the feature point from the normalized image,then extract the watermark.