The Resarch Of Image Authentication Based On Digital Watermarking

Digital watermarking is the technology that can protect copyright of digital products and maintain the safety of data effectively. It is an important branch of the information hiding technology. Image authentication based on digital watermarking, which has the advantage different from digital signature, is the hotspot in the field of information authentication. In this paper, the development of authentication watermarking (fragile watermarking & semi-fragile watermarking) is studied. The background and basal frame are dissertated. Based on the analysis of the fragile watermarking and semi-fragile watermarking algorithms and comparing their advantages and drawbacks, three schemes are proposed.A new method of distilling abstract is proposed in scheme one. Theory analysis and simulation show that the method can get short abstract and higher probability of change when the inputs change comparing with methods of Hash parity and Hash-hamming weight. Based on the method, a new fragile algorithm is proposed. Theory and simulation prove that the scheme is efficient to keep the use of image, improve the precise of tamper detection and location. On the other hand, it is simple, safe and applied.The method in scheme one is expanded to semi-fragile watermarking in scheme two. Firstly, a new image pre-processing method is proposed, which makes image resist JPEG compression. Secondly, based on applying the pre-quantization theory, the watermark is embedded in AC coefficients in DCT domain, which can get the original watermark after image compression. The scheme can distinguish compression from tamper, locate tamper and get high probability of tamper detection. The realization of the scheme is simple and safe, and the experiment results prove that it is validity. Otherwise, a new location method —region and cross location is proposed. The method can reduce error effectively.Based on the previous research, the semi-fragile watermarking in DWT domain also is studied.