Application the synchronization method of adaptive-observer.

This study discussed one of the types of synchronization method, the method called adaptive-observer, this method was applied to a type of Chua circuits, known as attraction - repulsion, the case of synchronization succeeded in the circuit when the transmitted variable was X1m and the coefficients of the coupled system were identical. When the parameters of the two couple systems differed, we noticed no synchronization. We also discussed the effect of the correlation strength factor (feedback gain) on achieving synchronization in the chaotic circuit. As we found that increasing the value of the correlation coefficient leads to the absence of interference between the sent and the received signal, as well as reducing the error rate and the speed of synchronization between the two systems, but in the case of mismatch of the coefficients, the state of non-synchronization remains the same even if we increase the correlation coefficient to d = 200. The success of the state of perfect synchronization led us to implement a secure communication system as well as a system for encrypting images using the chaotic system. The strength of the encryption was tested by the chaotic system using histogram, entropy in addition to the correlation coefficient, space key and key sensitivity, which all showed the high security of the encryption used. [ABSTRACT FROM AUTHOR]