Design And Implement On Audio Secure Communication Of Chaos System Based On FPGA

The chaotic signal is the signal that is generated by a deterministic system and has the characteristics of hard prediction, randomness similarity and so on. It is neither periodic nor symmetrical and not just a simple disordered state. It is also sensitive to the initial conditions. In recent years, the chaotic communication technology, which chaos study is gradually applied to has aroused widespread concern and developed rapidly. The design and implementation of chaotic communication systems can be achieved by using the digital signal processing devices such as digital signal processor (DSP) and field programmable gate array (FPGA). The strict matched parameters between the transmitters and receivers of the system can be achieved through precise mathematical calculation, which greatly improves the system performance and has become a development direction of the present field of chaotic communications. This paper focuses on the design and implement of the audio secure communication of chaos system based on FPGA in a laboratory environment, the main works of the thesis are listed as the following:(1) The Lorenz key sequence is generated by using FPGA. Lorenz chaotic system is a continuous-time system that cannot be directly processed by using FPGA. In the design, the system is first discretized by using simple Euler algorithm. Then the real numbers in the discretization equation are processed by using the combination form of fixed-point decimal and cut-bit computing so that they can be calculated correctly in the FPGA. Finally, the timing simulations show that the Lorenz chaotic key sequence can be generated to meet the demands of chaotic communication under the required design rate.(2) A feedback driving-response chaotic communication system is realized based on the synchronization principle of driving-response and feedback chaotic masking technology. On the basis of the realization of Lorenz key sequence, a series of encryption processing modules are realized by using the VerilogHDL hardware description language, which is combined with traditional cryptosystem, encrypting the digital audio information into the chaotic key sequence. The generated cipher text sequence is on one hand used as the iterative input of the driving system, and on the other hand to generate the decryption key sequence at the receivers in the response system. The system solution is proved to be feasible through m-sequence and the transmission testing experiment of parallel testing signal. Based on this, it is confirmed that the information theft cannot properly obtain the useful information in the case of unknown key sequence through comparative experiment test. (3) A chaotic audio communication platform is realized. The audio processing chip WM8731provided by Altera DE2development board is used in this design, the analog audio signals are converted to digital signals input by writing the configuration and interface code. After transmission in the chaotic communication system, the signals are reduced to analog audio signal under several different modules. Through final experiment, the transmission of the audio signal is proved to have a high degree of fidelity.