Research On Digital Watermarking Algorithm For TIN DEM

TIN DEM data is suitable for multi-resolution modeling of complex terrain composed of discrete points and widely used in many fields such as military affairs, surveying and mapping and so on. With the stepping into the digital era, the access, processing and dissemination of TIN DEM become increasingly convenient and efficient while the data security issues are getting more and more serious.As an advanced technology in the field of information security, digital watermarking technology provides a feasible way to protect the security of TIN DEM data. By analyzing the data feature of TIN DEM, the technical feature of TIN DEM watermarking and application requirements, the digital watermarking algorithm for TIN DEM is researched intensively in this dissertation. The main research results are as follows:(1) Based on the data feature of TIN DEM, the technical feature of the digital watermarking for TIN DEM is analyzed and the corresponding attack technology is classified. Then the impact on watermarking algorithms caused by the mode of data editing is discussed, which lays a solid foundation for the establishment of watermarking algorithms.(2) On the basis of the visible watermarking model based on the mesh density, a general visible watermarking algorithm for TIN DEM is proposed. Meshes in the region of watermarking information on the model surface is refined by applying the projection and polygon clipping algorithm so as to embed watermarking information. The proposed watermarking algorithm is suitable for the TIN DEM which is constructed according to arbitrary rules.(3) Via adjusting the rendering method of the visible watermarking model based on the mesh density, a visible watermarking algorithm for Delaunay triangular network DEM is proposed. By studying a generation method of the specified edge, the problem that it is unable to generate specific edge directly is solved. Then, the visible watermarking information is embedded into the model by using the generation method of the specified edge iteratively. The proposed algorithm embeds the visible watermark effectively and maintains data accuracy well.(4) According to the Nielson norm, a watermarking algorithm for TIN DEM which is robust to geometrical attacks is proposed. The watermarking embedding primitive of the algorithm is designed based on the feature of Nielson norm. By an improved quantitative mechanism, the watermarking information is embedded and watermarked primitives are labeled. The experiment results show that the proposed algorithm is capable of resisting the attacks such as translation, rotation, scaling etc.(5) On the basis of the watermarking algorithm for TIN DEM resistant to geometrical transformation attacks, a watermarking algorithm robust to splicing attacks is proposed. On the condition that the watermarking information to be detected is accessible, the noncontiguous watermarking embedding primitives are excluded from the watermarking embedding primitives group with the maximum correlation coefficient by using the adjacency between watermarking embedding primitives. On the opposite condition, the watermarking embedding primitives which contain consistent watermarking information are assembled. The proposed algorithm is able to detect watermarking information embedded in each sub-data, so the robustness to splicing attacks is obtained.