Research On Secure Communication Technology For IOS-oriented Mobile Terminal

With the development of the mobile communication technology and intelligent terminal product,the number of mobile communication users continues to grow,and smart phone becomes an important carrier for mobile communication.Voice call and SMS are important ways for people to communicate with their smart phones,hence the security of voice calls and Short Messaging Service(SMS)is very important.IOS is known for security and is favored by users.However when users use the iOS terminal for SMS and voice communication,they still face many security threats.Communication data can not only be intercepted by hackers through network interception,but also can be intercepted by Apple Inc.and other network operators.For example,Snowdon has exposed that Prism project could monitor all telephone communication system of appointed country,in which communication data of voice call and SMS on iOS terminal can also be intercepted.Hence,secure communication technology for iOS deserves more in-depth research.The purpose of this thesis is to propose and implement the secure communication scheme of voice and SMS on iOS system,and to ensure the communication contents of voice call and SMS without being intercepted by other third parties during transmission.In this thesis,we systematically do some researches on secure voice call and SMS for iOS system,and realize a voice encryption system based on VoIP architecture and a SMS encryption application on an iOS system,which can ensure communication data of voice call and SMS to avoid being intercepted by other third parties during transmission.The voice encryption system is composed of self-developed sercure VoIP server(SVServer)and iPhone voice encryption terminal-Secure VoIP Phone Special(SVPhone-S),which can support the following two sets of call scheme.The one is iPhone end-to-end confidential call scheme(iE2E-SCS)and the other is iPhone single-ended confidential call scheme(iSE-SCS).The iE2E-SCS is applied in the scene when both sides of the communication are equipped with SVPhone-S to ensure that the call voice data is encrypted and transmitted between the both sides and the communication data of voice call will not be intercepted by other third parties in the whole course.The iSE-SCS is the extension of iE2E-SCS,to ensure that the communication data of the SVPhone-S is encrypted and will not be intercepted by other third parties when only one side of the communication is SVPhone-S.The SMS encryption application-Secure Message(SMessage)will be installed on the iPhone to transfer message confidentiality int the whole course.Before each message is sent,SMessage system generates a specific session key to encrypt the message and attaches a hash value to the cipher text message.SMS receiver verifies the hash value,and decrypts the SMS after verification passed.In this way,the SMS encryption application achieves SMS encrypted transmission with once a secret and ensures the SMS will not be intercepted by other third parties in the whole course.The main contributions of this thesis are as follows:Firstly,we design and implement iE2E-SCS and iOS voice encryption terminal-SVPhone-S.The iE2E-SCS can achieve voice encryption transmission between the SVPhone-S.The methods of two-way authentication and key agreement are designed by studying SIP protocol stack,RTP protocol and key agreement algorithm.The SVPhone-S is implemented by programming for iOS system based on belle-sip of open source SIP library,oRTP of open source RTP library.Secondly,we design and implement iSE-SCS and Secure VoIP Server-SVServer.The iSE-SCS is applied for the scene when only one side of the communication is equipped with SVPhone-S,to ensure the voices sent and received by SVPhone-S are encrypted.The authentication and key agreement methods are designed by studying the work process of VoIP server.The SVServer is implemented by C language programming based on open source Asterisk architecture.Thirdly,we design and implement SMS encryption application-SMessage based on iOS.SMessage can achieve secure transfer of SMS.The methods of SMS encryption and secret key transfer are designed by applying AES encryption algorithm.The scheme is implemented by programming for iOS system,and the sending and receiving of SMS are realized by applying the iOS system library-MessageUI.Finally,performance tests for iE2E-SCS,iSE-SCS,SVServer and SMessage are made.The test shows that the iE2E-SCS scheme can realize the secure voice transfer between SVPhone-Ses.The phone connection rate reaches 99%,the key agreement success rate reaches 98%,encryption accuracy rate reaches 99.96%,and the voice clarity reaches 97.8%.Also,the iSE-SCS scheme can achieve secure voice call between SVPhone-S and non-encryption terminal.The phone connection rate reaches 98%,the key agreement success rate reaches 99%,encryption accuracy rate reaches 99.92%,and the voice clarity reaches 97.86%.In addition,the concurrency of SVServer is well done,when 1000 users login or 1000 calls connect at the same time,it can achieve a concurrent rate of 99%.Finally,SMessage can achieve correct encryption.The key agreement success rate and encryption accuracy rate both reach 100%.