Stream Cipher from Chaotic Systems and High Gain Observers

This paper proposes an advanced secured transmission of information method founded on synchronizing chaotic system with an optimal high gain observer. The challenging idea investigated in this work is to insulate the encryption process from the synchronization operations relying on the same chaotic system but with two different roles. First, the chaotic system is a part of the encryption process and generate pseudo-random sequence of signals, which will be treated with Exclusive-OR operations to form the cipher, and then the dynamic system will acts as a transmitter. In fact, the designed transmission scheme is established using an improved optimal nonlinear observer having the advantage to reconstruct the transmitter. Finally, the decryption operation is carried out by replacing the chaotic system by its estimation one. Numerical simulation based on an image encryption/decryption is conducted as an illustration to demonstrate the outstanding performances of the designed transmission method.