On Watermarking Technique Based On Chaos

Watermarking is newly-born technique for copyrights protection in recent years, and is an important branch of information hiding. The purpose of watermarking is mainly to prevent illegal large-scale copying of digital products and to trace them. In this technique, it is requested that only when the products become commercially valueless can the embedded watermark be removed, so excellent robustness and high secrecy are both required. Among the various classifications of watermarking, robust and non-blind image watermarking is mainly studied in this thesis. Secrecy of watermarking has been a hotspot. The applications of chaos, especially chaotic systems in watermarking are basically studied in the thesis, and chaotic systems are introduced to replace chaotic iterative mapping to improve the secrecy of watermarking for the first time. Many methods to produce secret keys with chaos are discussed in detail, and the characteristics of chaotic systems which can be utilized in watermarking are analysed in this thesis respectively in direct case and indirect case. Some other problems of using chaotic systems are all solved very well. At the same time of improving secrecy, for both the requests of robustness and invisibility, human visual systems are fully considered in order to realize self-adaptability of embedding in the thesis in both DCT and DWT cases. In order to face the new still image compression standard JPEG2000, the research work in the thesis is basically based on DWT.Some elementary knowledge on image processing is presented before the research of using chaos in watermarking begins. For the need of scrambling some images in latter work, Hilbert curve for image scanning is studied in depth, and a fast algorithm for it based on matrixes is presented in the thesis. All the research results are tested by digital simulations, and the tests shows correctness and feasibility of the research. Some new chaos and methods are adopted to study the secrecy of watermarking in the thesis, and resistance to foreign attacks of watermarking is enhanced with good robustness and invisibility.