应用泰森多边形的矢量地理数据零水印算法

A zero-watermarking algorithm for vector geographic data based on Thiessen polygons

传统嵌入式水印算法会对原始数据的精度造成影响,为满足高精度矢量地理数据版权保护需求,本文提出了一种应用泰森多边形的矢量地理数据零水印算法。首先,对矢量地理数据进行归一化预处理,采用Douglas-Peucker算法提取矢量地理数据的特征点,并构建特征点的泰森多边形;然后,根据每个泰森多边形与相邻多边形周长的大小关系,确定其特征位为1或0,运用泰森多边形周长与原始水印之间的哈希映射值,确定该特征位在序列中的位置,特征序列中每一位可能会有多个不同的特征位对应,利用投票原则确定该位置的最终值;最后,将特征序列与置乱后的水印图像序列进行异或运算,生成零水印。研究表明,该算法能够抵抗平移、缩放、旋转、裁剪和简化等常见攻击手段,具有较强的鲁棒性。这可为高精度矢量地理数据版权保护提供技术参考。

With the continuous improvement of Internet technology,the methods for acquiring vector geographic data have become increasingly diverse,effectively addressing people’s daily needs.However,the impact of its illegal reproduction and distribution cannot be underestimated,it not only damages the legitimate rights and interests of data owners,but also presents a potential threat to China’s national defense and security.Digital watermarking technology offers a solution by converting copyright-related information into a watermark signal and discreetly embedding it within the host data.This incorporation makes the copyright information an integral part of the host data,rendering the watermark information difficult to remove when the host data is subsequently utilized.In cases of copyright disputes,digital watermarking technology allows for the extraction of copyright information from the host data.Consequently,digital watermarking technology can be used as a reliable technical means for safeguarding data security.Traditional digital watermarking technology embeds copyright information into the vertex coordinates of host data without impinging on the data’s regular usage.However,in practical applications,due to the low redundancy of high-precision vector geographic data,embedding copyright information can compromise data accuracy.The emergence of zero watermark technology effectively addresses the shortcomings of traditional watermark methods.This technology,grounded in specific data characteristics,generates copyright protection information,which is registered within a third-party intellectual property rights(IPR)library for storage.Subsequently,data watermark detection is facilitated.Suspicious data encounters prompt the use of,zero watermark technology to extract the copyright information of suspicious data,enabling a comparison between the copyright information of the suspect data and the original data,thereby resolving data copyright ownership disputes.In order to meet the needs of high-precision vector geographic data copyright protection,a zero watermarking algorithm for vector geographic data using the Thiessen polygon is proposed.Firstly,the vector geographic data is normalized and preprocessed,and the Douglas-Peucker algorithm is used to extract the feature points of the vector geographic data and construct the Thiessen polygon of the feature points.Secondly,according to the size relationship between the circumference of each Thiessen polygon and the adjacent polygon,determine its eigenvalue as 1 or 0,and use the hash map value between the circumference of the Thiessen polygon and the original watermark to determine the position of the feature bit in the sequence,each bit in the feature sequence may have multiple different feature bits corresponding to each other,and the voting principle is used to determine the final value of the position.Finally,XOR the feature sequence with the scrambled watermark image sequence to generate a zero watermark.Experimental results demonstrate the algorithm’s efficacy in withstanding common attacks such as translation,scaling,rotation,cropping and simplification.The algorithm displays strong robustness,providing technical support for copyright protection of high-precision vector geographic data.