With the rapid growth of the Internet and wireless communications, people make extensive use of portable wireless devices to access information such as voice, data and multimedia, any time from any place, enjoying ubiquitous services. IP multimedia subsystem (IMS) are regarded as the total solution for packet-switched networks, combining wired and wireless infrastructures, providing a standardized interface for information services. We propose the IMSKAAP key exchange protocol and fit it into the IMS session initiation procedure to achieve media plane end-to-end security. This mechanism also mitigates the impact of spam over IP telephony (SPIT) using mutual authentication, fulfilling the lawful interception requirement. The simulation result shows that the proposed mechanism provides a more secure session key exchange and does not need the additional message exchange cost. The voice call end-to-end delay is also lower than the hop-by-hop security associations defined by 3GPP.
