The Research Of Speech Secure Communication System Based On Chaotic Theory And Speech Recognition Technique

Chaos is a kind of complicated and random phenomenon that is determined wholly by deterministic nonlinear system. In recent ten years, chaos theory and application research are widely paid attention to and have become a hotspot in international academy. The secure communication systems that apply the chaotic signals have strong anti-decryption and long unpredictability. Speech recognition technique investigates the human-computer interaction, and it can also be applied in the field of communication. In recently years, speech recognition technique also gets swift development. The combination of speech recognition technique and speech chaotic secure communication can strengthen the security of the speech secure communication system, and it has theoretical significance and important practical value.In the thesis, the history and the existing circumstances of chaotic dynamics, chaotic secure communication and speech recognition are reviewed. The several important problems of chaotic secure communication, including the basic concepts of chaos, chaotic synchronization technique and the methods of chaotic secure communication are systematically analyzed. And the common course of speech recognition is also presented.The main research contents in the thesis are listed as below:1. Aimed at the brushless DC motor chaotic model, the two methods based on Gerschgorin theorem and state observer are separately used to achieve chaos synchronization. Based on that step,two approaches to establish the chaotic speech secure communication to achieve the speech signals'secure transmission are brought forward. The first method is making use of the synchronous chaotic sequences generated from the brushless DC motor and the state observer to directly mask the speech signals to be transferred. The other method is improving the direct masking method. First, encrypt the speech signals, and then carry out chaotic modulation and...