A SURVEY OF CHAOTIC SECURE COMMUNICATION SYSTEMS

Secure communication using synchronization between chaoticsystems(chaotic secure communication, for short) is a new concept ofsecure communication. The great potentials of this kind of “hardwarekey” secure communication systems had driven the progress of thisfield rapidly. Since 1992, chaotic secure communication had evolvedfour generations. In this paper, a detailed history of chaotic securecommunication systems is given. The disadvantage of the first threegenerations of chaotic secure communication schemes is low efficiencyof channel usage. To overcome this disadvantage, a chaotic communicationscheme, which belongs to the fourth generation, using impulsivesynchronization of chaotic systems is presented. In this paper,impulsive synchronization of two chaotic systems is reformulated asimpulsive stabilization of a synchronization error system to the origin.Based on the theory of impulsive differential equations, we presenttheoretical results on the asymptotic synchronization of two chaoticsystems by using synchronization impulses. An estimate of the upperbound of impulse interval is given for the purpose of asymptotic synchronization.The robustness of impulsive synchronization to additivechannel noise and parameter mismatch is also studied. We concludethat impulsive synchronization is more robust than continuous synchronization.Combining both conventional cryptographic methodand impulsive synchronization of chaotic systems, we propose a newchaotic secure communication scheme. We use this new chaotic securecommunication scheme to transmit a speech signal. Computer simulationresults based on Chua’s oscillators are given.