Hyperchaos Qi System Construction And Chaos Communication Based On Switch-modulated

The research has studied the hyperchaos Qi system construction and digital chaos secure communication based on swith-modulated using the methods of theoretical derivation and numerical simulation as follows:(1) A four-dimensional hyperchaotic Qi system is obtained by adding linear term and nonlinear term of nonlinear controller to Qi chaotic system. The hyperchaotic Qi system is studied by bifurcation diagram, Lyapunov exponent spectrum and phase diagram. Numerical simulations show that the new system's behavior can be periodic, chaotic and hyperchaotic as the parameter varies.(2) A scheme for digital secure communication is proposed by using control function which is defined by two communicants based on chaos synchronization and chaos masking. Different driving signals can be sent according to the promissory transmission situation of control signal, then transmission field which is consist of protocol and transmission content is produced, which will enhance the complexity and decrease the correlation of transmitted signals. Meanwhile, by designing compound nonlinear function transformation for transmitted signals to further intercalate the secret key, a determined intruder is very difficult to retrieve the contents of message signal using forecasting method. Theoretical analysis and numerical simulation result show that this method is effective.(3) A scheme for digital secure communication is proposed by using control function which can achieve self-control encryption and decryption based on chaos synchronization and chaos shift keying. Both communications sides at sending and at receiving can adopt many kinds of encryption and decryption schemes. Firstly, by utilizing different control signals, we can choose different encryption functions at sending. Secondly, we can restore the control signals at receiving, and then the corresponding decryption function can be automatically chosen. It will enhance the complexity and decrease the correlation of transmitted signals. Meanwhile, by designing compound nonlinear function transformation for transmitted signals to further intercalate the secret key, a determined intruder is very difficult to retrieve the contents of message signal using forecasting method. Theoretical analysis and numerical simulation results show that this method is effective.