  The third generation partnership project (3GPP) has addressed the feasibility
of interworking and specified the interworking architecture and security
architecture for third generation (3G)-wireless local area network (WLAN), it
is developing, system architecture evolution (SAE)/ long term evolution (LTE)
architecture, for the next generation mobile communication system. To provide a
secure 3G-WLAN interworking in the SAE/LTE architecture, Extensible
authentication protocol-authentication and key agreement (EAP-AKA) is used.
However, EAP-AKA have several vulnerabilities. Therefore, this paper not only
analyses the threats and attacks in 3G-WLAN interworking but also proposes a
new authentication and key agreement protocol based on EAP-AKA. The proposed
protocol combines elliptic curve Diffie-Hellman (ECDH) with symmetric key
cryptosystem to overcome the vulnerabilities. The proposed protocol is used in
hybrid coupled 3G-WLAN convergence network to analyse its efficiency in terms
of QoS metrics, the results obtained using OPNET 14.5 shows that the proposed
protocol outperforms existing interworking protocols both in security and QoS.
