Chaos synchronization applied to secure communication via sliding mode control and norm state observers

In this paper, we have assumed that the parameters of a unified chaotic system are time-varying, uncertain and only the output variable is available for feedback. Due to its robustness to parametric uncertainties and fast transient responses, a sliding mode control strategy is introduced to globally synchronize two of these chaotic systems, i.e., the initial conditions of master (transmitter) and slave (receiver) systems are arbitrary. This result also allow us to solve the problem of secure communications by using the chaotic nature of the unified attractors, where the proposed formulation based on norm observers and time-varying cryptographic keys increases the security level of the approach. Simulation results illustrate fast synchronization and less vulnerability properties of the new communication scheme.