| The third generation (3G) mobile communication systems provide large coverage, completed subscriber management and nearly universal roaming. It also has high speed mobility. Nevertheless, 3G systems are subject to the low data rates. WLAN (Wireless Local Area Network) provides hot spot coverage with high data rates (up to 54Mbps while 802.11 a/g), but is subject to short range (reaches 100m the furthest) and lacking a roaming and mobility support. From users' point of view, the integration of WLAN and 3G systems will provide a convenient and attractive way for user to access network.Currently, the research of integrating WLAN with Cellular mobile networks has become a hot topic. Integrating 3G system and WLAN networks may offer subscribers high-speed wireless data services and ubiquitous connectivity. However, while integrating WLAN and 3G, there are still some security problems remained in terms of authentication and security. How to enhance its security is also very important for the development of the integrating system.In this thesis, Firstly, we analyze the security features and requirements of WLAN and its development is briefly introduced. Secondly, the security mechanism used in 3G system are discussed. Thirdly, we put emphases on the discussion of security problems in 3G-WLAN interworking. The related background and security technologies are also described. Then the six scenarios and two kinds of architectures for the interworking system are discussed briefly. Moreover we review the authentication protocol used in the integration of 3G and WLAN network, and point out its merits and flaws, and then improve it's drawbacks. After analyzing the defects of symmetric key based authentication scheme, we argue the advantages of the public key based scheme for wireless network. Using EAP-TLS protocol, the public key based authentication scheme for integrating network is presented to improve the security of EAP-AKA. Finally, a brief conclusion and future works are given . |
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