The Encryption Algorithm Research And Its Implementation On Digital Walkie-talkie

Digital walkie-talkies with strong anti-interference capacity,good voice quality,efficient bandwidth,high flexibility and ease of integration,are the most popular mobile terminals in the professional mobile communication.It is mainly used to the departments and enterprises with high command and dispatch functions.For the public security and military,which have high demand of confidentiality.In order to prevent eavesdropping in the voice information transmission,it is of great signification to research the voice encryption in the digital walkie-talkies.So that the voice is transferred with the form of ciphertext.In this thesis,we focus on the chaotic encryption technique,and have proposed a digital walkie-talkie voice encryption method.We design a voice encryption algorithm based on chaos theory.Chaos is a kind of movement seemingly stochastic,generated from nonlinear determined systems,so it can be used to design fast and secure encryption algorithm.In recent years,chaos theory has been widely concerned by academia.The main research works included as follows:1.Firstly,we introduce the present situation and trends of voice encryption of digital walkie-talkie,discussing the relationship between chaotic theory and traditional cryptography.Then learning the related theory of the chaos and chaotic algorithm’s design method.Finally,a digital walkie-talkie encryption system based on STM32 hardware is proposed.2.For voice encryption,a hybrid chaotic system with variable parameter is designed based on Logistic map and Hénon map.It is analysed from following respects mainly: initial sensitivity,correlation,Lyapunov index and randomness.The analysis results show that the hybrid system can generate key sequence with good randomness,which can be used for voice encryption.Then a voice encryption algorithm is proposed,encryption and decryption are realized on the MATLAB platform.The results show that the algorithm has characteristics of enough key space and fast encryption speed,which can satisfy system’s demand.3.On this basis,a real-time voice encryption method for digital walkie-talkie is proposed.Firstly,a encryption algorithm based on linear congruence generator and hybrid chaotic system is proposed.And the hybrid chaotic system is composed of Chebyshev map and Cubic map.Then,we proposed a vocoder module based on AMBE vocoder and CSP1027 codec,realizes the functions of voice signals’ s collection and compression,and makes the processing delay satisfy the cryptosystem’s demand.Finally,the chaotic voice encryption algorithm is implemented on the STM32 platform,and the voice encryption and decryption is completed.The results show that the encryption system has high security and good real-time performance.