Enhancing Security for Chaos-based Communication System with Change in Synchronization Manifolds' Delay and in Encoder's Parameters

In previous works, the chaos synchronization of multi-delay feedback systems with multi-feedback driving signal has been examined and used for designing a secure communication system. By utilizing the feature that one master can synchronize with slave(s) on multiple manifolds, a new scheme of modulation technique was proposed, i.e., synchronization manifold shift keying. In that secure communication system, the value of parameters and that of delays are kept constant in operation. In this paper, the methods which might be used for attacking the proposed secure communication system are discussed and schemes to enhance the security by means of change in the value of encoder's parameters and that of manifolds' delay are presented. As a result, the secure communication system can resist from existing breaking methods and future ones. The numerical simulations demonstrate and verify the effectiveness of these schemes.