| Along with the development of communication technology and the rapid popularization ofcommunication network, people gradually pay more attention to the cellphone’s security in theprocess of communication. Once the important national defense, military, government or businessinformation leaked, the national will get significant loss. Nowadays people are considering appliedchaos to the cryptography field, because chaos has some basic characteristics which make a naturallink with cryptography such as aperiodic, sensitive to the initial values and long-termunpredictability, etc. Chaotic encryption technology has significant development in recent years,even the most difficult of the realization of the chaos control and synchronization technology is alsoin application, making it secure communication, information, etc. which implies a good prospect.DSP’s process information fast, programmable properties is widely used for voice informationprocessing, image/graphics processing, military secure communication. Huawei’s WCDMAcommunication module MU103, support voice, text messages, data services and other business, aswell as the standard AT command set and Huawei extended AT command set. This paper, taking theabove as the background, combined the 3G technology, DSP, with chaos encryption technology, anddesigned a mobile secure communications solution.This paper includes the following aspects:(1) Basic theory of chaos and the latest progress of encryption technology were studied. On thebasis of Sprott system, a new Sprott chaotic system was constructed, and its’fundamental dynamics,including dissipative, balance, stability, Lyapunov index and bifurcation diagram, were analyzed. Achaotic analog circuit was designed and implemented on the EWB. Experiments showed that theexperimental attractor phase diagram was same with the simulated one.(2) Based on the structured chaotic systems, proposing a continuous chaotic system discreteand quantitative method to produce the required number of chaotic communication pseudo-randomsequence. And in help with the TMS320VC5509 of TI Company as core chip, combining with CCSdevelopment environment, had the process of discrete and quantification. Using the softwarepackage STS which was put forward by NIST（National Institute of Standards and Technology）totest the sequences, and the results showed that Sprott chaotic sequences had good performancefigures. It can be applied to the encryption systems.(3) The system was divided into two parts: voice processing and voice transmission. Voiceprocessing was implemented by the DSP, and the transmission was achieved in the use of MU103.In voice processing part, multimedia digital voice codec TLV320AIC23 was used to accomplish the A/D transform its sampling frequence was 8kHz, and each sampling point was 16 bits, and thesignals which had been discreted was processd with TMS320VC5509. Using the G.729A speechdecoding standard to compress and encode the voice signals, coding rate is 8kb/s. Then using digitalchaotic sequence which was generated by DSP to encrypt encoded voice signal, and the encryptionalgorithm was XOR. Changing the parameters k of the chaotic system and the initial value can getthe different key. Under the same parameters, the same initial value and the same number ofiterations, the chaotic system can produce the same key. Then using GPRS link to pass theseparameters in order to achieve synchronization.(4) In the voice transmission part, Huawei 3G module MU103 was used to establish GPRSlink. MU103 module access to the GPRS network firstly, then connected to the Internet networkwhich was established on the server, and the server transfered the voice data, And then the voicetransmission was achieved. And then the voice transmission was achieved.(5) The performance of the system was tested. And test results showed that the confidentialityof the system was well. The factors that affect system performance was analyzed, and found outsome factors, such as coding rate is 8kb/s, and baud rate of MU103 is 115.28kb/s, and thetelecommunications network transmission speed 472kb/s, and voice sampling frequency 8kHz, etc. |
PDF Full Text Request