In this paper, a method to enhance the dynamic characteristics of one-dimension (1D) chaotic maps is first presented. Linear combinations and nonlinear transform based on existing chaotic systems (LNECS) are introduced. Then, a numerical chaotic map (LCLS), based on Logistic map and Sine map, is given. Through the analysis of a bifurcation diagram, Lyapunov exponent (LE), and Sample entropy (SE), we can see that CLS has overcome the shortcomings of a low-dimensional chaotic system and can be used in the field of cryptology. In addition, the construction of eight functions is designed to obtain an S-box. Finally, five security criteria of the S-box are shown, which indicate the S-box based on the proposed in this paper has strong encryption characteristics. The research of this paper is helpful for the development of cryptography study such as dynamic construction methods based on chaotic systems.

In this paper, a new matrix projective synchronization for chaotic (hyperchaotic) maps is proposed. The novel scheme called P-M synchronization is presented in this paper, since it combines two matrix projective synchronization schemes (one is based on the invertible matrix P, and the other is based on matrix M). Compared to the regular matrix projection synchronization, the required matrix of the proposed scheme don't change with different master systems. Under the framework of classical Lyapunov stability theory, a state feedback controller is selected to realize global synchronization. In addition, simulation results are reported, to highlight the capabilities of the P-M synchronization proposed in this paper. Finally, a speech secure communication scheme based on the P-M synchronization is implemented, implying the P-M synchronization can be applied into secure communication filed.

In this paper, a new 3D discrete hyperchaotic system is constructed, and its Lyapunov exponent and approximate entropy are calculated. We adopt the drive-response method and self-adaptive method to make the hyperchaotic system to reach synchronization, and then design an encrypted transmission system based on the synchronization of this discrete hyperchaotic system. In the synchronous hyperchaotic system, the initial value related to the hash value of the speech signal of the chaotic system is designed. Some security analyses are studied in detail.

We propose an adaptive radial basis (RBF) neural network controller based on Lyapunov stability theory for uncertain fractional-order time-delay chaotic systems (FOTDCSs) with different time delays. The controller does not depend on the system model and can achieve synchronous control under the condition that nonlinear uncertainties and external disturbances are completely unknown. Stability analysis showed that the error system asymptotically tended to zero in combination with the relevant lemma. Numerical simulation results show the effectiveness of the controller.

In this study, it is proposed that a new matrix projective synchronization of fractional-order (FO) chaotic maps in discrete-time. A new synchronization error is introduced and a control law is constructed, which makes the synchronization error converge towards zero in sufficient time under the stability theory of linearization method of FO systems. Numerical simulation results are presented to illustrate the feasibility of the scheme. Finally, a secure communication scheme based on FO discrete-time (FODT) systems was proposed.