Research On Robust And Semi-Fragile Digital Watermark

With the rapid development of network techniques and multimedia processing tech-niques, digital works face a huge challenge in copyright protection and content authenticity.Robust and semi-fragile digital watermarking technique becomes an important solution. Inthis dissertation, robust and semi-fragile watermarking system is focused on. The humanvisual system (HVS), watermark detection and counter-geometric attack in the robust digi-tal watermarking system and the content authentication in semi-fragile digital watermarkingsystem are studied. The main research results are listed as follows:(1) Two robust watermarking schemes based on HVS are proposed, one of which isbased on block adaptive factor and the other of which is based on 3D HVS. The factor is aHVS using non-zero number of the quantized coefficients which represents the texture of animage. On the basis of this HVS the robust non-blind and blind watermarking schemes aredesigned. Using the idea that the gray-level image is extended to 3D space to embed water-mark, the corresponding 3D HVS is given and the blind watermarking scheme is designed.The experiments prove the validity and the robustness of two schemes.(2) Two detection schemes are proposed, which are respectively the correlation detec-tion scheme which point to the general multiplicative embedding rule and the multiplicativeoptimum detection scheme based on the classification of content. The correlation detectionscheme uses the independent relation between transform coefficients and watermark signaland the optimum detection scheme uses the principle that the different content leads to thedifferent distribution model and similar content leads to similar distribution model. Thetheoretical analysis, performance analysis and experiment proof of the correlation detectionscheme check its validity and robustness and the comparison experiment of the optimumdetection scheme proves the improvement of its robustness performance.(3) The counter-geometric attack semi-blind digital watermarking system is proposed.On the basis of this system, the watermarking scheme based on the comer points is pro-posed. This system uses the information of the watermarking cover to register the attackedwatermarking cover, and achieves the robustness of blind detection against signal process-ing attack and semi-blind detection against counter-geometric attack. This watermarkingscheme achieves the robustness of the geometric attacks after exactly estimating the geo-metric parameters by matching the comer points. (4) The multi-feature watermarking authentication rule is proposed. According to thisrule, the multi-feature watermarking authentication rule is proposed. This rule is proposedby comprehensively analyzing the security of multimedia authentication scheme from thepoint of view of the authentication set. The proposed authentication scheme extracts globalfeature and local feature from the coefficients of the lowest frequency and the middle fre-quency in DWT domain, respectively. Global watermark and local one implement the semi-fragile authentication. The security of this scheme is analyzed in detail.Finally, some open issues in present relative digital watermarking systems as well asthe future work are presented.