Encryption and decryption of information in chaotic communication systems governed by delay-differential equations

We consider different ways for encryption and decryption of information in communication systems using chaotic signal of a time-delay system as a carrier. A method is proposed for extracting a hidden message in the case when the parameters of the chaotic transmitter are a priori unknown. For different configurations of the transmitter the procedure of information signal extraction from the transmitted signal is demonstrated using numerical data produced by nonlinear mixing of the chaotic signal of the Mackey–Glass system and frequency-modulated harmonic signal.