Watermarking Algorithm For Raster Geographic Data In Network Lossy Transmission

The rapid development of Internet technology and WebGIS has promoted the transformation of raster geographic data sharing methods from offline distribution to online services,which greatly facilitates the transmission and application of data.At the same time,in the process of raster geographic data network sharing,the open network environment also breeds illegal activities such as data piracy and infringement,which has seriously violated the legitimate interests of the data owners and brought threats and challenges to the information security of the country and society.If only relying on traditional cryptographic techniques and related laws and regulations,it is difficult to effectively curb the occurrence of such illegal phenomena,and it is impossible to trace the origin of data after discovering illegal data.Therefore,there is an urgent need for an effective technology to provide comprehensive copyright protection for raster geographic data under the network environment.As a cutting-edge technology in the field of information security,digital watermarking technology accompanies the whole life cycle of data from production to distribution and application,and can provide comprehensive and effective protection for the copyright of digital data.The digital watermarking technology is an effective solution to the network security problems faced by current raster geographic data.At present,research on digital watermarking for raster geographic data has achieved some research results.However,the existing research results are mainly designed for the traditional offline distribution environment.The data sharing methods are mostly lossless disk copies.The particularity of the network environment is that its transmission mode is often lossy,and the data will be subject to multiple attacks such as compression and scaling in the transmission process.The transmitted data has a certain image distortion compared with the original data.However,the existing watermarking algorithms are generally difficult to resist the composite attack of compression and scaling,and it is difficult to satisfy the robustness requirement of lossy transmission of the network,resulting in various problems such as false detection,missed detection in the watermarking detection.In order to solve the problem of copyright protection for raster geographic data during network sharing,this paper focuses on the lossy transmission of the network and studies the digital watermarking algorithm for raster geographic data.The main research contents and conclusions are as follows:(1)The way of raster geographic data transmission in network and its security problems are discussed.The characteristics of raster geographic data watermarking technology and the impact of network lossy transmission on raster geographic data quality are analyzed.On this basis,a network transmission protection mechanism based on digital watermarking technology is established,which lays a theoretical foundation for the protection of raster geographic data in the network environment.(2)For network lossy transmission,a raster geographic data watermarking algorithm based on DCT and template matching is proposed.The algorithm realizes the conversion between copyrighted plaintext characters and pseudo-random sequences,which is based on Unicode encoding.On this basis,the watermarking information is embedded by modulating DCT coefficients,and the method of template matching is used to achieve the synchronization between the watermarking information and the embedding position,which improves the robustness of the algorithm.The algorithm has good resistance to JPEG compression,clipping,scaling and other conventional signal processing,and can play an important role in the copyright protection of raster geographic data during network transmission.(3)For network lossy transmission,a raster geographic data watermarking algorithm based on scaled normalization and parity quantization is proposed.The scale normalization method is used to establish the mapping relationship between the watermarking information and the embedding position.It has scale invariance and can effectively resist scaling attacks.On this basis,the watermark information is embedded by the parity quantization rules,which has good fault tolerance,and the compression attack is effectively resisted by the help of most principles.Through the combination of scale normalization and parity quantization,the algorithm can effectively resist composite attacks,which combines compression and scaling,and can realize blind detection,which can satisfy the demand of network lossy transmission.