A Survey of Chaotic Secure Communication Systems

Secure communication using synchronization between chaotic systems(chaotic secure communication, for short) is a new concept of secure communication. The great potentials of this kind of “hardware key” secure communication systems had driven the progress of this field rapidly. Since 1992, chaotic secure communication had evolved four generations. In this paper, a detailed history of chaotic secure communication systems is given. The disadvantage of the first three generations of chaotic secure communication schemes is low efficiency of channel usage. To overcome this disadvantage, a chaotic communication scheme, which belongs to the fourth generation, using impulsive synchronization of chaotic systems is presented. In this paper, impulsive synchronization of two chaotic systems is reformulated as impulsive stabilization of a synchronization error system to the origin. Based on the theory of impulsive differential equations, we present theoretical results on the asymptotic synchronization of two chaotic systems by using synchronization impulses. An estimate of the upper bound of impulse interval is given for the purpose of asymptotic synchronization. The robustness of impulsive synchronization to additive channel noise and parameter mismatch is also studied. We conclude that impulsive synchronization is more robust than continuous synchronization. Combining both conventional cryptographic method and impulsive synchronization of chaotic systems, we propose a new chaotic secure communication scheme. We use this new chaotic secure communication scheme to transmit a speech signal. Computer simulation results based on Chua’s oscillators are given. c ©2003 Yang’s Scientific Research Institute, LLC. All rights reserved. Received by the editors April 20, 2002 / final version received April 22, 2003.