Key Management Protocol for Roaming in Wireless Interworking System

3GPP makes efforts to enable usage of 3GPP system functionalities such as SIP calls between mobile terminals and 3GPP systems via the WLAN and to utilize 3GPP system functionalities to complement the functionalities such as charging means, authentication, authorization, and accounting functions available in the WLAN. And an interworking framework to integrate the services of 3G, WLAN and WiBro networks is proposed by Electronics and Communications Research Institute. Since each network adopts deferent protocols for mutual authentication and key agreement between users and networks, unified authentication for the integrated system is not simple problem when a user moves from one network to another. In this paper, a secure and efficient key management protocol for roaming among different networks is proposed.