Digital Communication Using a Novel Combination of Chaotic Shift Keying and Duffing Oscillators

In this paper, an improved technique for constructing Chaotic Shift Keying (CSK) for transmitting digital signals is introduced. In contrast to the classical methods where only two chaotic attractors, representing logic 0 and logic 1 are used to build CSK, the proposed system allows the chaotic transmitted signal to alternate among four different chaotic attractors. In addition, the transmitter parameters are used to implement a novel XOR-based encryption function to scramble the secret message. This has the effect of effectively hiding the secret message and providing better security and privacy against intruders’ attacks to the public communication channel. The parameters of the transmitter are assumed unknown, and are estimated at the receiver side to accomplish two tasks. The first one is to complete the synchronization process, while the second one is to decrypt the secret message using the duality property of the XOR-based digital function. A Duffing oscillator with smooth cubic nonlinearity is used to build the proposed system, where both synchronization and parameters estimation are carried out using an adaptive Lyapunov-based control approach. Simulation results are provided to illustrate the performance in both time and frequency domains using a single time series. Finally, recommendations for improving the performance are provided via discussing tuning of the control parameters and suggesting different ways to meet hardware constraints when transmitting real-time signals.