一种支持篡改定位的电子航海图零水印研究

本文针对电子航海图（ENC）使用过程中面临的数据安全问题，结合S-57标准下CRC校验和完整性认证需求，提出了一种顾及点位篡改定位特性的电子航海图零水印算法。该算法在分析ENC物标（要素）中以经纬度表示的离散点位坐标数据分布规律的基础上，构造离散点经纬度坐标数据校验码生成模型，结合离散点经纬度坐标数量对ENC单元格网进行二叉树分块处理，并分块解算基于离散点经纬度坐标校验码的二值序列，通过该二值序列与置乱加密后的水印图像进行异或操作构造零水印图像。算法中离散点的经纬度坐标校验码和格网分块技术的引入，在保证ENC数据精度和满足CRC校验的同时，具备点位篡改定位的特性。试验结果表明，该水印算法具有良好的稳健性、不可见性和一定的篡改定位精度，适用于电子航海图数据的版权保护。

Research on zero-watermark of electric navigational chart for tampering localization

In view of the data security problems in the application of ENC, combined with the integrity certification requirements of CRC checksums under S-57 standard, a zero watermark algorithm for ENC is proposed which takes into account the characteristics of point tampering. Based on the analysis of the distribution law of the discrete point coordinate data represented by longitude and latitude in the ENC object standard (element), the algorithm constructs the generation model of the longitude-latitude check code, and combines the number of the discrete point to carry out the binary tree block processing of the ENC cell network, and solves the binary sequence based on the longitude-latitude check code of the discrete point by block column and scrambled encrypted watermark image are XOR operation to construct zero watermark image. In the algorithm, the introduction of the grid block technology and longitude-latitude check code can ensure the accuracy of ENC data and meet the CRC check sum, and it has the characteristics of point tampering location. Experimental results show that the watermark algorithm has good robustness, invisibility and a certain degree of tampering positioning accuracy, which is suitable for copyright protection of ENC.