The Research Of Watermarking Technology For Engineering Graphics Copyright Protection And Tamper Localization

With the development of enterprise informatization, two-dimensional CAD engineer-ing graphics have been widely used in various fields of mechanical, civil engineering, sur-veying and mapping and costume design. CAD has significantly improved the efficiency ofproduction, but those products can be easily copied and modified, so copyright protection ofengineering graphics is threatened. Traditional file encryption and digital signature can’tsolve those problems, the digital watermarking technology has been extensively studied inrecent years as a new effective measure of copyright protection and content authentication.Current digital watermarking technology in image, audio and video, grids and other areashave been developed more mature, but in the field of two-dimensional CAD drawings stillin its infancy. However, CAD engineering graphics as a main carrier of enterprise designinformation, copyright protection and content authentication is also very meaningful.In this paper, the basic principle and the domestic and oversea research situation ofdigital watermarking technology are introduced briefly. Current watermarking algorithmsfor CAD engineering graphics do not consider the characteristics of graphic primitives andthe obvious disadvantage of these techniques is that they are severely weakened by lowtransparency, poor robustness and inaccurate tamper localization. This paper proposes aneffective watermarking algorithm for CAD engineering graphics. Firstly, the watermark se-quence is circularly extended. Then, the watermark is successively embedded into a scalefactor of the adjacent graphic primitive. Watermark extraction is an inverse process of wa-termark embedding and the correct watermark information can be obtained from the ex-tracted watermark sequence by statistical analysis. Comparing the extracted watermark se-quence with the theoretical embedding values, the integrity of the graphics can be verifiedand the modified part can be located accurately.Experimental results show that the proposed algorithm has good invisibility and ro-bustness, not only can be immune to translation, rotation and scaling operations with iden-tifying precise scaling factor, but also resist modification, deletion and addition of primi-tives and other malicious attacks with high robustness, while tampering localization can beachieved precisely and can specify the type of modification.