Method for Protection of Copyright on Vector Data

Abstract

The paper proposes a method of copyright protection for vector maps, based on the embedding of raster digital watermarks. The method combines original ideas, namely, a vector data watermarking approach that does not distort the coordinate information of vector objects and embedding of noise-like images that encode a binary sequence. The use of noise-like carrier allows to simplify the verification procedure, and also to ensure the resistance of the hidden bit sequence to distortions, including interpolation errors. In comparison with previous investigations made by the authors when solving problems of vector data protection, the robustness of the embedded noise-like digital watermarks has been significantly increased by developing a new algorithm for detection of the binary sequence hidden in the spectrum of a noise-like image. The purpose of the experimental studies was to assess the attainable probability of correct sequence extraction for various parameters and embedding conditions. The study of information capacity showed that the potential amount of information embedded in each polygon without distorting the watermark sequence depends on the type of a map, namely on the number of vertices that make up each polygon. An experimental study on robustness against potentially possible transformations aimed at maliciously deleting the digital watermark from the vector map is performed. The developed method demonstrates resistance to affine transformations, cropping, addition, removal and reordering of vertices / objects, and, thus, seems to be the optimal solution to the problem of copyright protection for vector data. The analysis of the method quality according to the criteria of accuracy, durability, information capacity, and computational complexity is performed. The results of all conducted studies confirm the efficiency and the effectiveness of the proposed method for vector map protection, as well as its distinct advantage over the prior art.