Research On The Watermarking Algorithms For Vector Tile Data

In recent years,with the rise of SOA,cloud computing,big data analysis and other technologies,a new generation of service-oriented WebGIS has developed rapidly,and interactive maps have become a hot spot.Compared with raster tiles,vector tiles have many advantages,such as clear topological relationship,small amount of data,infinite scaling and strong interaction.They meet the needs of interactive operation and spatial information analysis of geospatial data,and are an important direction of the development of network maps.Vector tile data is made up of vector geographic data and is an important basic information resource and achievements in survey and drawing.However,in the network environment,the security situation of vector tile data is more severe.The fragility of vector tile caching mechanisms,the legibility of client code,and the aggression of web crawlers bring great security challenges to the protection of vector tiles data.Therefore,a technology is urgently needed to achieve the balance between tile data sharing and tile data copyright protection.Digital watermarking is a cutting-edge technology in the field of information security and can effectively solve the security problems faced by vector tile data.Compared with traditional vector geographic data,single vector tile data is smaller,watermarking capacity is limited,attacks are more complex and diverse,multi-user splicing is more common,and the possibility of multi-user collusion is greatly improved.Higher requirements are put forward for digital watermarking technology.Based on the characteristics of digital watermarking for vector tile data,the digital watermarking algorithms for vector tile data have been studied.The work and results in this article are as follows:(1)Based on the spatial characteristics,manifestations and application environments of vector tiles,the data characteristics of vector tiles are analyzed.The single-user and multi-user attack modes faced by digital watermarking for vector tile data are analyzed and summarized.The properties of digital watermarking for vector tile data have been proposed and the evaluation criteria have been given from the aspects of watermark capacity,data fidelity,robustness and collusion resistance.Based on the above,a digital watermarking model for vector tile data is proposed.(2)From the perspective of the watermark capacity,the relationship between quantization index modulation and watermark capacity is deeply analyzed.The upper limit of watermark capacity of a single coordinate point is calculated under the constraint of the allowable error and the lowest effective precision bit of vector tile data.Combining the spatial characteristics of vector tile data,a new quantization mechanism is proposed.The quantization index modulation is based on two-dimensional grid division,which makes full use of the embedding space of coordinate points.Experiments show that the proposed large watermark capacity algorithm effectively improves the watermark capacity,and can resist many attacks.(3)In view of the problem that vector tile data is vulnerable to multi-user collusion attack,in the stage of watermarking generation,the collusion attack models,Tardos codes and its length optimization scheme are deeply analyzed,and Tardos codes is applied to the network distribution of vector tile data.In the stage of watermarking embedding,considering the spatial characteristics of vector tile data,the influence of quantized index modulation on different attack models is analyzed,and the q-ary encoding capacity optimization is proposed.Based on this optimization mechanism,the optimal scheme of combining Tardos codes with quantization is selected.In the stage of watermark extraction and detection,aiming at the vulnerability of vector tile data to multi-user splicing attacks,a watermark extraction and detection method against multi-user splicing is designed to improve tracking performance.The relationship between watermarking capacity and collusion resistance is studied by analyzing the encoding mechanism and experimental methods.Experiments show that the proposed anti-collusion vector tile digital watermarking algorithm has strong robustness and better imperceptibility.