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Chaotic Synchronization And Its Application In Image Encryption

Posted on:2015-12-24Degree:DoctorType:Dissertation
Country:ChinaCandidate:H J LiuFull Text:PDF
GTID:1108330482955746Subject:Computer application technology
Abstract/Summary:PDF Full Text Request
Since the theory of chaos control and synchronization were proposed, they played an important role in the fields of secure communication and image encryption, which make chaotic synchronization and its application become a hot spot in the research of chaotic theory. Although we have made some progress in the study of chaotic synchronization control method, the theory of chaotic control and synchronization is not perfect. Several methods of chaotic control and synchronization need to be further improved. In this paper, the research status of the theory of chaotic synchronization and its application in recent years is summarized and analyzed. A hybrid synchronization scheme based on single linear controller is proposed for integer order chaotic systems. Three projective synchronization methods are proposed in view of the fractional-order chaotic system. Two different image encryption algorithms are proposed based on chaos theory and hybrid synchronization method, respectively. Simulations have been carried out to guarantee the security and efficiency of proposed cryptosystems. The main work of the research is reflected in the following aspects:(1) Because the existing hybrid synchronization schemes have the problem of poor generality, a hybrid synchronization scheme is proposed for all the chaotic systems with symmetry. Taking the unified chaotic system as an example, a linear controller for hybrid synchronization is presented, and theoretical analysis and simulation experiments show that hybrid synchronization can be achieved in the case that only one of the three dimensions is controlled. When the single linear controller is added in the second dimension, as long as the value of control gain is large enough, the hybrid synchronization can be realized. If the value of control gain is greater, the implementation of hybrid synchronization will be faster. When the single linear controller is added in the first dimension, the control gain is neither too big nor too small. If the linear controller is added in the third dimension, in addition to hybrid synchronization, adjusting the initial system value of chaotic system or the size of control gain can achieve complete synchronization.(2) A modified projective synchronization method based on the OPCL coupling method for fractional order chaotic system is proposed. The method introduces the OPCL coupling method into the synchronization of fractional-order chaotic system. Based on the stability theory of linear fractional-order systems, modified projective synchronization of two different incommensurate fractional-order systems or commensurate fractional-order systems with mismatch parameters is achieved. The advantage of the method is its high synchronous speed and strong robustness.(3) For chaos synchronization of different dimension of fractional order system, a modified function projective synchronization method based on reduced-order and added-order is proposed. An adaptive controller and a parameter update law are designed to achieve modified function projective synchronization between two fractional order systems with different dimensions. At the same time, the unknown parameters of the response system can be estimated accurately and quickly.(4) The outer synchronization of complex networks with multiple fractional order chaotic systems is discussed. Based on adaptive synchronization control method, the modified projective outer synchronization between two fractional-order complex networks with different nodes and different topological structures is realized. Based on stability theory of nonlinear fractional order system, the sufficient conditions are proposed, which are also applied to the case with the same topological structure. Numerical simulation results show that the larger the order of chaotic systems and control gain are, the faster the speed of the complex network synchronization is.(5) An image encryption algorithm based on extended 3D cat map is proposed. The two dimensional Henon map and improved Logistic mapping are used to generate the control parameters of 3D cat maps. The position scrambling and pixel value replacement are combined to encrypt the gray image. Simulation experiments with multiple gray images show that the encryption scheme has good encryption effect and has the ability to resist the statistical analysis attack. In addition, another image encryption algorithm based on hybrid synchronization method is proposed. The approximate entropy algorithm is introduced to analyze the complexity of hybrid synchronization of chaotic system, which demonstrates that its complexity is higher than a single chaotic system. Therefore, if the time series generated from hybrid synchronous system are used in image encryption, higher security will be obtained, which has been verified by several experimental results and safety analysis.
Keywords/Search Tags:Chaos, Fractional-order chaotic system, Complex network, Hybrid synchronization, Projective synchronization, Image encryption
PDF Full Text Request
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