Design And Implementation Of Encrypted VOIP Based On Digital Certificate

As the development of the Internet and network basement construction,the application based on the Internet is getting more and more popular because the maturity of the technology and cost advantages.The technology of voice communication goes through GSM,CDMA,4G and so on.But the security of voice communication has not been focused.The risk of eavesdrop,temper,terminal pretending is still serious.In this paper a network telephone project is designed which is based on the certificate authority,RSA cryptology algorithm which cannot be brute force attacked,DH key agreement algorithm which cannot be intercepted and AES cryptology which is efficient for media data.These provide the system the characteristics of anti-intercepted,anti-force attack,anti-fake-terminal.Besides,a UDP protocol is used to decreased the time delay.There are three innovation points in the project.These are the usage of digital certificate,as the infrastructure,the combination of DH and asymmetric,and the specific application protocol based on UDP.The author designs and develops the following 6 modules:(1)UI:Mainly responsible for rendering and jump on interface,creating the UI system on the mobile platform,which is the user interface to the telephone and certificate management.(2)Certificate Management:Certificate applying,cancellation,deleting binding equipment and so on,which makes the basic safety layer of the system.(3)Encryption:Making the encryption and decryption work for the voice data and control messages,as well as verify the signature function based on the certificate module.(4)Network:NAT LAN traversing,and fill the reliable transmission protocol for control module and the unreliable transmission of audio package.(5)Centre Control:Which is based on the certificate management module,to control the flow of information and voice in the form of encryption,including dialing control and exception management.(6)Media:For audio data recording and the audio data playing.All modules above is designed and implemented by author independently.After a series of post-test found that the system can make great protection from fake identity,tampering and eavesdropping.Some function is also made mobile-optimized on Android.The project can provide an effective reference for future developing and researching on VOIP security.