A Switching Chaotic Circuit Based Color Image Encryption Methodon

With the rapid development of modern communication technology,the security of color image information has become a hot topic in the field of communication.In order to ensure the secure transmission of color images,people have conducted extensive research on encryption algorithms.Due to its extreme sensitivity to initial conditions,pseudo-randomness,and ergodicity,chaos has a significant advantage in the field of encryption.Compared with the parametrically determined chaotic systems,chaotic circuits with the perturbation of the parameters of electronic components can introduce pseudo-randomness into their original dynamic characteristics.Therefore,their dynamic characteristics is more abundant and they can provide a larger key space.The size of the key space is a core measure of cryptographic performance.In this thesis,an integer-order switching chaotic circuit and a fractional-order switching chaotic circuit are designed by using the parameter perturbation of electronic components and the infinite switching operations.The chaotic property of the designed chaos circuits and its rich dynamic characteristics are verified by the circuit simulation.Two encryption algorithms are designed and the chaotic encryption sequences obtained by the above chaotic circuits are respectively used to encrypt the color images.Matlab numerical analysis confirms the effectiveness and superiority of the encryption schemes based on the above two types of chaotic circuits.The main contents are as follows:Chapter 1,an integer-order switching chaotic circuit is designed.By connecting the drain and source of an insulated gate field effect transistor with the linear resistor in the driven Chua's circuit,the output resistance of the field effect transistor in series with the above linear resistor.By using a variable of Chua's driving circuit to control the gate and the source of the field effect transistor,the purpose of utilizing the ergodicity of chaos to make the output resistance of the field effect transistor appear a complicated dynamic changing process is achieved.Furthermore,the equivalent linear resistance in the driven Chua's circuit is changed to a time-varying resistor.The encryption algorithm is designed based on the combination of pixel scrambling and pixel substitution,and then the encryption of the color image is completed.Chapter 2,fractional order systems have advantages over integer-order systems for modeling physical phenomena in nature and component constraints of devices because the former have more complex dynamic characteristics and more degrees of freedom than the latter.The above design method is extended to fractional order,and a fractional-order switching chaotic circuit is designed based on the Chua's drive circuit and the driven Chen circuit.What is different from the integer-order switching chaotic circuit is to exchange the linear resistance in the driven Chua's circuit described above with a resistor in the unit circuit of fractional impedance of the driven Chen circuit.Furthermore,a resistor in the unit circuit of fractional impedance of the driven Chen circuit is changed into a time-varying resistor.The encryption algorithm is designed based on the combination of original image pixel scrambling,dense image pixel scrambling and diffusion transform,and then the color image is encrypted.