Research Of Dynamic Encryption Methods On VoIP

VoIP is the product of public telephone network combined with IP network,it is an advanced technology that can transfer the voice over the internet,but there are some hidden dangers when VoIP provides services.The traditional telephone network (PSTN) provides services safely because of its closure,and it is difficult for attackers to eavesdrop on the line directly.But the VoIP is open,there are a variety of ways for user to access it easily on the internet,so the security of communication can not be guaranteed.In recent years,there are many specialists and scholars,at home and abroad,put forth many methods about how to transmit the voice safely.Many technologies,such as the chaos theory,the information hiding technology etc,have been applied in some experimental systems.Cryptography is the most commonly used technology,and the approach is to make the telephone work with an encryption machine together.This thesis,based on the approach,introduces a dynamic encryption method on the division of voice to increase the complexity of encryption and the security of communication by choosing the encryption algorithms and allocating the keys dynamically.Traditional methods of encryption,no matter symmetrical or asymmetrical encryption system,always encrypt the whole message with the same algorithm,and then increase the length of key,or the rounds of encryption to enhance the security of communication.According to the real-time feature of VoIP,the article abandons the method which used to encrypt the full text of documents before,and introduces a new one,that is dynamic encryption on the division of voice.Firstly,dividing the voice into several groups,in order to reduce the quantity of the voice and increase the speed of encryption;on the other hand,it can make the encryption dynamic by selecting some different algorithm to encrypt these groups.In addition,the random number generator can generate a random key,and disorder it by dynamically shift processing before distributes it to the groups.Finally,uses a digital envelope which has a high security to ensure the transmission of the key.In this thesis,some operations" such as division,encryption,which used before the transmission of voice,prolong the time of communication.So the problems:the standard size of divisions,the delay caused by the encryption comes out.The article chooses the software SJphone as a platform,and defines the classes that used in the module of encryption.As the former problem,this article will use Matlab(a mathematical software) to find the optimal division by optimizing the experiment results;as the delay problem,we will construct a experiment environment and use a delay testing software to measure how long the delay caused by the encryption will be and trying to shorten it.Because of the limitation of time and equipment,the research still remains at the stage of simulation.The size of divisions as well as delay problem is still need future study and optimization.