A Copyright Protection Scheme For Vector Maps Based On Cloud Models

With the great development of geographical information systems (GIS) and information technology, digital maps are gradually replacing their analog counterparts. Digital maps are easy to use but not secure. They can be copied and spread with low cost and high speed and this makes piracy often occur. Many digital watermarking schemes have been proposed to solve this problem. Vector maps, one kind of digital maps, also have copyright protection problems. Hence, it is essential to protect the copyright using digital watermarking schemes.Firstly, the background and current research status of digital watermarking are introduced. Then theoretical knowledge of digital watermarking and vector maps are presented including theoretical basis of digital watermarking, theoretical basis of vector maps and existing digital watermarking mechanisms for vector maps. Key technologies that protect the copyright of vector maps based on cloud models are then introduced. These key technologies are composed of cloud droplet watermark, embedding position selection and secure container design. Finally, a scheme for protecting the copyright of vector maps based on cloud models is proposed after in-depth analysis of current copyright protection schemes for vector maps.Current schemes for protecting the copyright of vector maps based on cloud models only embed pairs of normal random numbers generated by cloud model into the original vector maps without considering self-protection and characteristics of vector maps. The invisibility and robustness of these schemes are not very good. In this paper, using the characteristics of discrete wavelet transform (DWT) and file driver technology, a novel copyright protection scheme for vector maps based on cloud models is proposed. Firstly, DWT is used to transform the spatial data of vector maps. By selecting the appropriate positions from the DWT coefficients, the watermark generated by the cloud model under the control of secret keys of user is embedded into the selected DWT coefficients. Finally, whether the extracted watermark is the original one can be judged by the comparison results of similar clouds.Experimental results demonstrate that this algorithm can not only protect vector maps itself, but also cause little disturbance on the original map's accuracy. Besides, it is robust against common attacks such as compression and filtering.