Design And Implementation Of Digital Encryption Telephone Based On AMBE-2000 Vocoder

With the fast development of public information system, people pay more attention to the information security. As the most popular communication tool, telephone communication needs to be encrypted because it's often used in some special occasion. The common telephones mostly send analog signals which are hard to be safely encrypted. So the digital encryption telephone will be widely obtained in the future.The paper takes the encryption technology in the digital encryption telephone as the research object. It raises the new key generating and key managing method which adapts to the digital encryption telephone. It also improves the AES algorithm in order to fit the different output data rate of vocoder.This paper analyzed the characteristics of the voice communication system firstly. Based on these characteristics it raised how to choose the symmetric cryptograph algorithm and non-symmetric cryptograph algorithm. It studied the key generating and key managing method which adapt to the digital encryption telephone and improved it. The keys of symmetric cryptosystem and non-symmetric cryptosystem change on every connection. The telephone which is called runs the ECC key generating program and sends the public key back to the telephone which is calling. Then the calling telephone generates the session key, encrypts the session key by the public key and sends encrypted session key to the telephone which is called. It also improved the standard AES algorithm. The improved AES algorithm can deal with the input data group of different length automatically. And the system was experimented and analyzed by voice examples and has got some satisfying results. It described the hardware structure of the digital encryption telephone. And it gave the interface schema and whole PCB circuit diagram.