| As one main aspect of nonlinear science, chaos has been got much attention by lots of researchers of various fields, and it has comprehensive applications in natural science and social science. Chaos synchronization is an important research direction of chaotic science. It has attracted great interests since 1990's, and much progress has been got in its applica-tions such as secret communication and image manipulation, chaos synchronization phe-nomena have been observed in more and more domains such as life science, economy and physics recently, in which the systems don't have the same structures. How to study chaos synchronization between different systems becomes an acute problem, and its concerned work is very little up to now. With the development of network and multimedia, it is more and more important for information security of multimedia. Considering the deficiencies of traditional cryptography, people begin to search for new methods for multimedia informa-tion protection. Among them chaos based digital watermarking shows its advantage, and may be a new efficient mean for multimedia protection.Chaos synchronization between two different chaotic systems is mainly studied in this dissertation. Linear coupled synchronization,active control,adaptive control methods are employed in theoretical analysis and simulations of synchronization controller design, a kind of controller designs for synchronization of different uncertain chaotic systems are mainly studied. Furthermore, chaos based digital watermarking algorithms are studied and simulated. The main contents are as follows.The concepts of chaos and chaos synchronization are reviewed firstly in this disserta-tion, and the present researches of chaos based digital watermarking are generalized and summarized in detail.Three different kinds of chaos synchronization schemes are studied between two Chen chaotic systems: Linear coupled synchronization and active control synchronization methods are employed when system parameters are known, the range of feedback gain ma-trix coefficients for coupled synchronization is given, and the controllers of active control synchronization are designed, which are very simple, and the synchronizing convergent speed is rapid; adaptive control method is employed when system parameters are unknown, to implement complete synchronization of Chen chaotic system, one controller and three controllers are designed respectively, and the corresponding parameter adaptive laws are also derived.The chaos synchronization between two different chaotic systems via active control is also studied in this dissertation. The designing idea of active control is given, Genesio and Chen chaotic systems,Unified chaotic system and Genesio chaotic system are taken as examples to illustrate the designing method of controller for active control synchronization, the designing scheme is simple, different chaotic systems can be exponentially synchronized asymptotically with designed controller.The synchronization between two different uncertain chaotic systems via adaptive con-trol is studied in this dissertation. A common theory for adaptive control synchronization design is given. Genesio chaotic system and Chen chaotic system,Unified chaotic system and Genesio chaotic system,Modified Chua's circuit and Lorenz chaotic system,Modified Chua's circuit and Lu chaotic system are taken as examples to illustrate the designing method of adaptive controllers Based on Lyapunov stability, and parameter update laws are also derived, which solved the synchronization problem between two different uncertain chaotic systems.The synchronization between two different uncertain hyperchaotic systems is also studied in this dissertation. The synchronization controller and parameter update law be-tween hyperchaotic Chen chaotic system and generalized Henon-Heiles system are designed based on Lyapunov stability theory.A common designing method of generalized synchronization between two chaotic sys-tems is proposed in this dissertation, which can be applied to continuous chaotic system and discrete chaotic system. The generalized synchronization of Lorenz chaotic system,Rossler chaotic system and Henon map are designed.A novel chaos based spatial domain watermarking algorithm is proposed in this disser-tation. Different from most existing chaotic watermarking schemes, two kinds of chaotic maps are used to improve the security of the algorithm. A 2D chaotic map is used to encrypt the embedding position, and another 1D chaotic map is used to locate the pixel bit of the host image in which watermark bits are embedded, imperceptibility and robustness test of the proposed algorithm are performed in the end.Two chaos based frequency domain watermarking schemes are proposed in this disser-tation: one is the human visual system based watermarking scheme, watermark signal is embedded into the sub-low coefficients of blocked Discrete Cosine Transform(DCT)by taking full use of the properties of human visual masking, an adaptive image watermarking algorithm in DCT domain is implemented; another is a DCT phase based watermarking scheme, by considering the property that there exist much more informations in the phase components than that in amplitude components in DCT domain, so phase components are much more robust than that of amplitude components, a novel blind watermarking algorithm which embed encrypted watermark signals into blocked DCT phase is proposed.In the end, we make a brief summary on this dissertation and make a prospect for the further research.
|
PDF Full Text Request