Study Of Serval Security Issues Adn Key Technologies For VOIP Based On IMS Architecture 

IMS (IP Multimedia Subsystem) put forward all IP network architecture for multimedia applications. IMS realize mobility management, multimedia session signaling, carrier transport and end to end IP utilizing SIP. As an important development trend in telecommunications, VoIP faces with many new security risks. We further study the hardware and software for VoIP so that provide security solutions for VoIP networks.This paper studies several relative safety problems and keyt technologies First, this paper studies the architecture of IMS system, and then analyzes the IMS system security threats with special attention in the authentication and DdoS. Further more, this paper studies VoIP security issues.Second,this paper studies the security of IMS authentication mechanism and brings forword two-way HTTP-S/MIME authentication scheme based on virtual key ring which can reduce the high cost of the pki using. Communicating parties achieve mutual authentication through the responder's identification code and acknowledge contents generated by challenge; and execute data encryption, decryption, signature and verification utilizing the sender's key and session key. The solution combines with bi-directional HTTP digest authentication and S/MIME based on virtual key ring, thereby increases IMS security for multimedia applications without PKI mechanism.Finally, the paper analyzes the mechanism of denial of service, especially focused on SIP bombs, SIP-Cancel/Bye and attacks in connection with RTP, and proposes a multi-level measures to guard against denial of service.In the customer service system for"Doublecoin Holdings Ltd", these measures have achieved good results.