Automatic Switch Circuit Hardware Design Of Encryption System For Phone And Fax

Telephone and fax technologies are increasingly used, and security issues are more and more important within communication. This dissertation shows the progress on the early encryption system. This method has been evaluated in experiments. We have designed the hardware of th encryption system which can switch automatically between the encryption state and the decryption state.We design the telephone encryption system and fax encryption system separately. To improve the security of communication, an encrypt system based on 3DES algorithm is described in this dissertation. We have made losts of progress according to the users.We design the system whitch can work in decrypting way or in encrypting way. Both spekers use this system conveniently.The system can work in control of the MCU which can control other integrated circuits such as MODEM. The FPGA can make the decrypting digital singal into encrypting singals according to 3DES algorithm. The system can resolve the communition security problem. This telephone encrypt system has been implemented successfully and performs well, and can be used widely. The system has been validated on the PSTN (Public Switched Telephone Network). It has indicated that the voice transmitted is clear and that the quality and the speed of the fax is ensured to a haigh stand. In the meantime, telephones can still work as normally.