Power spectrum mask in chaotic secure communication

Chaotic secure communication is mainly realized by chaotic mask, namely, the information signal is masked by chaotic signal with wide spectrum. Some key issues in chaotic mask have been studied in-depth. As an example, the typical master-slave chaotic synchronization system based on the modified Chua´s circuit was introduced. The additive and multiplicative methods used in chaotic mask were deeply explored. The power spectral characteristics of the signal which was masked by chaotic signal were obtained through calculation and were deeply discussed. In conclusion, the two covered ways was summarized at the end of the paper, that the multiplicative method has better performances than additive method which requires the chaotic signal power should reach more than 10 times than the power of information signal to achieve complete mask.