In this paper, we propose a new lightweight authentication protocol with local security association (SA) control to locally authenticate an inter-domain roaming user efficiently based on its mobility and traffic patterns in mobile networks. We first design a protocol to establish a local SA for authenticating the roaming user securely. Then, in order to determine the life time for the local SA, an authentication cost function is proposed to evaluate the authentication efficiency with the

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... of risk, mobility and traffic patterns. The optimal life time of the local SA is determined by minimizing the authentication cost function. The performance of the proposed protocol is analyzed with respect to authentication cost under different mobility and traffic patterns. Comparing to DIAMETER, the proposed approach outperforms DIAMETER for macro-mobility users with high volume of authentication requests.