Abstract: In this paper, we present a secure communication method for a high-power information signal based on chaotic masking. In the transmitter, an adaptive controller is adopted to pick up the change of the information signal, and to inject the controller's error into the transmitting system. At the same time, the information is directly added to the chaotic signal in transmission to drive the receiving system. In the receiver, another adaptive controller is used to maintain chaotic synchronization of the transmitting and receiving systems and to recover the information signal. Since the synchronization error is independent from the information signal, the power of the information signal can be equivalent to that of the chaotic signal, and the frequency of the information signal can be set within the range of the principal frequencies of the chaotic signal. The results of theoretical analysis and numerical simulation show that the presented method not only enhances the degree of security of low-dimensional chaotic systems but also significantly improves the signal-to-noise ratio at the receiving end.

Key words: chaotic masking, secure communications, adaptive controllers, Chua's circuits