Digital Watermarking In Transform Domain With Its Applications

Digital watermarking technique is emerging as a cutting edge research field of information security in recent years. It embeds some information in protected digital object (such as static images, video, Audio, etc.) to verify the copyright and track violations. Watermark can be the author's serial number, company logo and so on, which could be used to identify the source and version of documents and images as well as the ownership from legal user. Such watermarking usually is unperceptable. It has a lot to do with original data and can bear some damages which do not destroy the value of original data. Digital watermarking involves the study of theory and technology in many areas, with an intensive theoretical fundament and flexible application.As For the universal application and the basic framework of digital watermarking methods, the research is deployed towards two directions: on one hand, the classic Quantization Model Of Watermarking In Frequency Domain is analyzed and how quantifying step size affects the visibility of watermark is discussed, and theoretic inferior limit of the peak signal-to-noise ratio (PSNR) is estimated for the watermarked image. These theoretical analysis results are verified by experiments. On the other hand, a watermarking algorithm based on coherence, which can embed watermark with modification of coefficient in LL channel using the domain coherence, is proposed. The watermark can be significative sequence or binary image and it can be recovered without original cover image,as well as good accuracy by utilizing Bayes classifier. Experimental results show the algorithm is invisible and robust to common distortions such as noises, filters, down-samples and JPEG compression.Additionally, in the practice of copyright protection, it is usually required to utilize the bits of information as most as possible. The same original object is often embedded more than one watermarks. After introducing the princinples of fragile watermarking, Taking advantage of lossless compression and error correction code, a multipurpose watermarking scheme is implemented and the simulation results demonstrate it not only has good robustness but also performs more accurate in tamper prompting.