Design Of Telephone Encrypting System Based On DSP

Recently, many wiretapping cases have occurred all over the world and the wiretapping rate has a rising tendency. It affects society's order greatly and brings many troubles even massive loss to the user whose information divulges. Because the traditional PSTN has very low security, especially in subscriber's line which transmits analog voice signal, the voice is very easy to be wiretapped by others. The telephone network has been constructed and impossible to use the new system to guarantee the security of information in a short time. In order to resolve this contradiction, we need to design a kind of system which must be transparent to the user and the network, and must guarantee that the telephone conversation content cannot be wiretapped by others.This dissertation introduces two solutions which base on FPGA and DSP separately, and then adopts the later on the ground of compare of the two solutions'characters. It will establish safe correspondence if both users set the same passwords before starting the correspondence. Users don't need to worry about that others can decrypt the encrypted voice data.The system uses TMS320VC5509 DSP producted by TI Co. as the main processor and adopts G.729a recommended by ITU and Rijndael as the coding and encrypting arithmetics separately. This dissertation introduces the structure of both hardware and software at first, and then implements the software modules of G.729a and Rijndael arithmetics, USB driver and drivers of other peripheries on TMS320C5509a DSP. In the end, a testing program developed on CCS2.2 (For C5000) takes a test of all the software modules and can run on SEED-TMS320VC5509DSK developing borad accurately. It indicates that the anticipating goal is achieved.In the course of system design, modularization method is adopted and all the software modules are independent one another. We can easily transplant the system into other domains such as faxes encrypting, IP Phone and private data network by changing the interfacing circuit and adding or deleting software modules.