Fuzzy-chaotic hybrid secure communication system modeling design and control

In this thesis, a new approach to design secure communication system is proposed that includes generation of chaotic masking signal and synchronization procedure which provides a higher level of security compared to traditional methods. Due to efficiency and accuracy requirements, combination of fuzzy logic and chaos theories was used to model uncertainty and complexity of real complex secure communication system. Complexity of this hybrid fuzzy-chaotic approach assures an increased level of security. Trade-off between complexity and security may be achieved by generation of transmitted information using fuzzy modeling of specific desired chaotic behavior in system. Works on the use of fuzzy chaotic masking of transmitted information and appropriate synchronization procedures to increase security level of communication system is considered in. This interesting property of fuzzy chaotic systems makes them very useful in secure communication systems. The considered problem is related to the use of important properties of chaos to establish secure communications. In view of this, two chaotic systems are required: a transmitter (master) system and a receiver (slave) system. Often, transmitter system adds message onto a chaotic signal. This type of encoding is referred to as chaotic masking. The receiver decodes the message by a subtraction between the transmitter signal and its generated copy. The most well-known nonlinear chaotic system is Lorentz system. We investigate in the thesis a fuzzy Lorentz system as system with fuzzy number-valued initial conditions and fuzzy parameters. In this case, trajectories of state variables will be described by fuzzy functions of time t. For synchronization of receiver and transmitter in the fuzzy-chaotic secure system time-reversed fuzzy Lorentz system and regular fuzzy Lorentz system are used. The fuzzy time-reserved system is considered as receiver system with fuzzy controller, and the regular fuzzy Lorentz system is regarded as transmitter system. Fuzzy controller provides synchronization of the receiver Lorentz system to transmitter one to get minimal error. To verify feasibility and effectiveness of suggested hybrid fuzzy-chaos secure communication system different transmitted is be investigated. To the best of the authors knowledge design of receive in fuzzy-chotic secure system was not considered in existing literature. In this paper solving et this problem is considered.