Design And Implementation Of Mobile Voice Encryption\Decryption Software On FPGA

The GSM system is a mature network. The safety of the voice transmission on the network should follow the specification of the network to achieve higher security confidentiality and to keep the existing GSM system. End-to-end encryption is encrypted before voice sending. The receiving party received speech signal after decryption.There are two kinds of approach to achieve end-to-end encryption of voice on GSM network.The first one is using network data channels. It has the advantages of a flexible manner and many technology. However,it also has some limitations.The second approach is using traditional voice channels. In comparison,the traditional GSM network through the voice channel encrypted delay smaller,and with the existing network of good business integration, is conducive to the existing users of the universal.Unlike CDMA system adopts the CELP coding method, the voice channels of the GSM system use RPE-LTP(Regular Pulse Excitation-Long Term Prediction,rules pulse excitation- long-term projections). The voice encryption algorithm that useing at RPE-LTP is rare.Therefore, this paper designed a new voice encryption algorithm. on the basis of analysing RPE-LTP vocoder working principle,this paper proposes the RPE-LTP coding algorithm that can be transmitted through traditional GSM voice channel voice encryption algorithm. On studying of the speech smoothing and filtering technology, the system adopted FPGA chip and VHDL hardware description language to implement a new anti-RPE-LTP coding voice encryption/ decryption algorithm. Completing module designs such as frame scrambling encryption,adding synchronization head, wiping off synchronization head and hashing decryption etc to realize voice encryption process.In the meantime, the voice algorithm simulation analysis the results. In addition to verify every module function, the voice algorithm verifies and analysis encryption process and decryption process of the whole system.in the result, the algorithm has advantages of both voice signal processing and block cipher encryption arithmetic.And it has good balance. In addition, the algorithm operates before the speech signal entering into the vocoder, it will not damage the phonetic characteristics of speech signal and it will restore the original signal at the receiving end. At the same time, the algorithm does not remould any equipment in the base station. It is a kind of voice end-to-end encryption method in the GSM network that has advantages of low cost and high efficiency.The design will complete in the company ISE14.2 Xilinx integrated development environment. The design will optimize the voice quality and reduce noise further.