1.Electronics and Telecommunications Research Institute, Daejeon, Korea; 
2.Penta Security Systems Inc., Seoul, Korea; 
3.Pukyong National University, Busan, Korea

In this paper, we propose the authentication mechanism for a handoff in cdma2000-WiBro inter- working environment. In the interworking environment, the handoff procedure requires the authentication on MS for the access control and the accounting. In the handoff procedure, it is required to perform the EAP-AKA authentication process with cdma2000-HN (home network) because TN (target network) does not have the in- formation for the authentication about MS. This process has relatively long delay. Therefore, the fast handoff authentication mechanism for reducing the long delay in the handoff procedure is needed. Thus this paper pro- poses the handoff authentication method of using the reactive context transfer and ticket forwarding method, to provide the fast handoff in cdma2000-WiBro interworking environment. The proposed scheme satisfies security requirements on handoff and has the advantage of low signaling overhead in handoff authentication.