Study Of Digital Watermark And Application In Software Copyright Protection

Digital watermark is a new direction in the information security field. It's a new technology which can protect copyright and authentication source. The author's personal copyright information can be embedded in the products. But we can't percept it, only special software can pick it up.In this dissertation, the application of digital watermark technology has been studied in the round. First of all, background,meaning,domestic and international current situation and problem of existing of watermark are described. Then, basic problems such as the essential feature and principle of the digital watermark, etc. are introduced. The basic frame of the digital watermark system is generalized. The common digital watermark algorithms at present are generality introduced. Subsequently, the preconditioning method of the watermark is introduced. The preconditioning of the grey level picture is mainly compression of the grey level picture and the shuffle technology of the picture. Then, the theory of wavelet transformation is recommended in detail. Finally, a new way for copyright protection on software is proposed.In this dissertation, grey level picture is watermark. The grey level picture is pretreated such as compress, shuffle and two value preconditioning; it is stalwart in order to strengthen the watermark. Consider the performance when the picture is resolved and recombined, select for use resolve coefficient Nr =2 and reconstruct coefficient Hd = 6 biorthogonal wavelet (Bior2.6). The original image is resolved into three layers and four belts by Bior2.6. The watermark is inserted into low frequency coefficient and intermediate frequency coefficient of wavelet. It use replacement not add when embedding. The algorithm conquers the shortcoming of using original image in the past and can be carried out more easily. The algorithm can be applied in a bigger field. Experiments results shows that this algorithm can against widely varying signal distortions (such as sharp, excision, distortion and Gaussian noise), compression and have good robustness. This system based on digital watermarking is of simple construction, and implement method is convenience. It has some reference value to protection of software copyright.