Information Hiding in Image Authentication

[[abstract]]Computer network and digitized information, which bring the convenience of spreading and modifying, make it much easier to acquire multimedia data. Therefore, it becomes more and more important to affirm the legal use of multimedia data to protect the security and credibility of shared data. Digital Watermarking, developing recently, has been proposed as an efficient way to authenticate the integrity of protected image. In the first part of this dissertation, we presented a multipurpose fragile watermarking technique that adopts JPEG-like compressed watermark prototypes. The prototypes among blocks are spread by toral automorphism with an asymmetric key structure. Furthermore, the watermark prototypes are disordered by a one-way hashing function and encrypted by a public-key encryption function to increase the security of watermarks. Finally, the watermarks are embedded to protect the integrity of images. The experiments show that the proposed scheme can correctly localize tampered areas and remedy them to the extent of JPEG-compression quality even when 50% of the image is cropped. In the second part of this dissertation, we proposed an adaptive watermarking technique that is robust to JPEG compression and sensitive to malicious manipulations. The watermarking technique includes three major functions: generating the content-based watermarks, hybrid watermarking, and calibrating. These watermarks are embedded using various strategies according to the characteristics of the DCT coefficients. Finally, two calibrating functions are used to increase the accuracy of authentication. Experimental results from the proposed scheme demonstrate that it is able to blindly localize tampered areas, robust to JPEG compression, and sensitive to malicious manipulations, including the counterfeiting attack.