Theory And Application Of Secret Communication Based On The Unified Chaotic System

In 1980s, people believed that chaos was uncertain and harmful. So at that time, researchers mainly focused on how to eliminate chaos by using control. And these researches led to a new research area"chaos control"and produced a lot of results. How ever from 1990s, people found out that chaos was actually useful and could be used to do many things. For example, chaotic secret communication is one of them.Chaotic signals have many useful features, such as Pseudo-randomness, Aperiodic, Continuous broadband spectrum, Similar to the noise, Very complex trajectories and Unpredictability. These features make it naturally hidden and suitable for secret communication as a carrier. For sender part, we encrypt information as waveforms or streams which have chaotic characteristics; for receiver part, we decrypt signals and regain correct information. Meanwhile, the sender part and receiver part should be chaotic synchronized in order to decrypt the signals correctly.The innovations of this paper were: The existing chaotic secrete communication mainly focused on communication between two people, this paper designed a secret voice communication system with finite members. The feature of the system is using the unified system to produce different kinds of chaos. The unified system was brought by Jinhu lv and Guanrong Chen in 2001. This chaotic system bridged between Lorenz system and Chen system and presented the whole chaotic system includes Lorenz system and Chen system. Accordingly, the unified system could produce different kinds of chaos with different parameter. By taking this parameter as key, we could let the members of the group communicate with each other. But the third part can not decrypt the information.Meanwhile, we realize the chaotic secret communication system on DSP. We chose TMS320VC5416 DSP STARTER KIT (DSK) which is a development platform and assessment tool for starters to develop our system. TMS320C5416 DSK contained a VC5416 board and an Integrated Development Environment--Code Composer Studio v2.1 IDE running on PC. VC5416 connected with PC by USB. Users could use Code Composer Studio (CCS) to program, compile and link to generate executable code which is downloaded to the target board's memory and run. Also, TMS320C5416 DSK contained a PCM3002 chip which is a 16/20 bit stereo audio codec chip produced by TI Company. PCM3002 sample analog signals through an audio input port and convert the analog signals to digital signals which could be processed by Microprocessor (DSP). Then the digital signals could be converted to analog signals and outputted by PCM3002.Finally, according to the features of the system, we provided some methods to resist noise which include: resist noise methods for DSP, communication channel, resist noise methods in software and void enhancement.