Design of an Analog Time-Varying Audio Cryptography System Based on Sliding Mode Synchronization of Non-identical Chaotic Systems Described with Time-Delayed Fractional-Order Dynamics

In this study, first, a comprehensive robust control approach is proposed for projective synchronization of chaotic systems with dissimilar structures, mismatched time delays, non-identical fractional derivative orders, uncertainties, and external disturbances based on fractional-order sliding mode control strategy and fractional-order Lyapunov stability theorem. The synchronized systems are then utilized to design an analog time-varying audio cryptography system, which can secretly send voice messages through insecure communication channels. Finally, the results of numerical simulations along with security analysis demonstrate that the designed audio cryptography system has more accurate and secure results and easier practical implementation than previous audio cryptography systems.