B. TURGUT
Fintek Inc., Eskisehir Yolu 4.km Ankara, Turkey

M. U. AGLAYAN
Department of Computer Engineering, Bogazici University, Bebek, Istanbul, Turkey

Third Generation mobile telecommunications systems enable multimedia services combining the growth in mobile communications with the growth of the Internet. On the other hand, WLAN's are easy to implement, cheaper to construct and provides high speed services compared with other wireless technologies. In order to achieve access independence and to maintain a smooth interoperation with wireline and wireless terminals across the Internet, security is an important issue that must be handled. One step to achieve interoperability may be providing secure interoperability between the 802.11 WLAN and 3G networks. Although both systems have authentication mechanisms in their own domain, there is not a single mechanism that provides seamless authentication between two domains. In this paper, an AAA based authentication mechanism is presented between 3G networks and 802.11 networks. The authenticaton mechanism provides seamless authentication between two domains using the existing authentication mechanisms in each domain and provides a way for distributing session key and encryption algorithm between 3G core network and 802.11 core network.