Research On Encrypted Voice Over Mobile Communication

Mobile communication is already the most widely used means of communication, including mobile phones and Internet voice chatting. An important objective in mobile communication systems is security speech communication. People enjoy the convenience of mobile communication technology, meanwhile suffer from various security weaknesses. The goal of this paper is proposing a feasible technology method for the communication between mobile devices. This method enables encrypted signal transfer over communication networks.The major contents of this paper are as followed:1. At first, this paper took a closer look at the module that converts the electronic version of speech signal into transmit channel. Starting from the model of human voice, then this paper figured out how linear predictive analysis synthesis lies at the very heart of mobile phone transmission of speech. Meanwhile, this paper considered the problem of transmitting encrypted voice signal through compressed voice channels such as those used in wireless communications networks. So, we concluded several key technical requirements of encrypted voice to ensure it can avoid voice activity detection.2. After that, this paper also came up with several different proposals based on voice processing technology, such as local language transfer based on voice recognition, a codebook permutation approach based on the wavelet analysis and the voice encrypted based on reverberation effects. Although failed several times with extensive MATLAB experiments, author gained valued experiment to drive the next move.3. This paper proposed an end-to-end encrypted voice communication system based on speech-like modulation. After pre-processed, an analog voice signal is first converted into a voice data stream including pitch, voicing determination, the best set of prediction coefficients errors by a chosen low-rate compression algorithm. Then we encrypted those data and transfer the series data into conversion to choose the excitation vectors in the codebook. Then superimpose them to the synthesis filter to get the final encrypted voice. The paper roughly estimates the error rates and gains the decode voice as result.4. This paper proposed a feasible way to solve the cipher steam synchronization. Voice communication transceivers use the ZUC steam cipher to provide the key. In order to realize the correct decryption in receiver, sender and receiver need to ensure consistent state key generator, namely key stream synchronization. For the ZUC stream cipher module and the SM3 algorithm module realized on the DSP, test results prove the correctness of the modules.