JSP电信电话计费系统设计(含英文文献翻译)
Security Aspects of 3G-WLAN Interworking
Geir M. Køien and Thomas Haslestad, Telenor R&D, Norway
ABSTRACT
Third-generation cellular systems will provide wide coverage and nearly universal roaming, but will not realistically live up to the bit rate expectations placed on them. On the other hand, WLAN systems already offer bit rates surpassing those of 3G systems, but are often found lacking with respect to roaming and mobility support. In short, WLAN systems are great for hot spot coverage, while 3G systems provide global coverage and the necessary network and management infrastructure to cater for security, roaming, and charging requirements. The focus of this article is on security aspects of 3GPP-WLAN interworking.
INTRODUCTION
Mobile systems like Global System for Mobile Communications/General Packet Radio Service (GSM/GPRS) are immensely successful. The flexibility associated with cellular telephony has gone from being a luxury to becoming a commodity. The present 2.5G systems like GSM/GPRS are capable of delivering IP services, but current cellular systems are still mostly used for speech services. Low bandwidth and expensive data services are perceived to be the main culprits.
Third-generation (3G) systems will improve data capacity and offer data rates up to 2 Mb/s and above, but it is unlikely that the user will be offered the full theoretical capacity since deployment cost is high. This is in contrast to the wireless LANs (WLANs), which www.youerw.com security measures and architecture beyond basic radio access.
Ideally, we would want the subscription management, roaming, and security facilities of a 3G system and the hot spot capacity and low investment cost of WLAN systems. Integration of the two systems therefore aims to combine them such that their best features are kept intact and their weaknesses mediated by the companion system. An important challenge is to reconcile and consolidate the security architectures of the systems.
BACKGROUNDON 3G-WLAN INTERWORKING
WIRELESS LOCAL AREA NETWORKS
WLAN is, in all simplicity, a cable replacement technology. It provides typical user equipment such as a personal computer with means to move freely within the borders of coverage while maintaining connectivity to the computers’ local are network.
IEEE Project 802.11 has provided us with the current WLAN market winning 802.11b standard. 802.11b is the standard for 2.4 GHz and provides bit rates up to 11 Mb/s on the physical medium. IEEE 802.11 also has the 802.11a standard for the 5 GHz band (UNII-band) that provides bit rates up to 54 Mb/s. Please refer to for useful overview of IEEE 802.11 WLAN technology.
ETSI Project Broadband Radio Access Network (BRAN) has published the HIPERLAN/2 standard. This standard provides a WLAN system for the 5 GHz band with integrated quality of service (QoS), security, and bit rates up to 54 Mb/s. Another flavor of WLAN, HiSWANa, also exists. MMAC HSWA is the Japanese organization behind the specification of HiSWANa. HiSWANa is a WLAN system for the 5 GHz band, with capabilities and design that resemble those of HIPERLAN/2. The WLAN community has formed a joint group called WLAN Interworking Group (WIG) in order to be unified on the issues of interworking.
Security-wise the three systems differ. The current IEEE 802.11b deploys confidentiality and integrity protection through a scheme called Wired Equivalency Privacy (WEP).WEP suffers from manual key management and is also cryptographically broken. HIPERLAN/2 and HiSWAN have more advanced confidentiality and encryption mechanisms. A new enhanced security standard is being specified for IEEE 802.11 that aims to provide enhanced and manageable access security.
THE 3GPP SYSTEM
The Third Generation Partnership Project (3GPP) is a global specification organization for telecommunication and comprises the following organizational partners: ARIB, CWTS, ETSI, T1, TTA, and TTC. Its original mandate was to produce a global specification for a 3G mobile system within the framework set by the International Telecommunication Union (ITU) called International Mobile Telecommunications 2000 (IMT-2000). The cellular system being specified within 3GPP, known as the Universal Mobile Telecommunications System (UMTS), has a new radio system and access network, extensive support for packet data and IP multimedia, and provides a host of other higher-layer services.
Cellular systems such as UMTS and GSM have excellent characteristics in terms of coverage and roaming. Roaming is one of the key factors when identifying reasons for GSM’success. The roaming network and its associated functionality, as we know it today from GSM and GPRS, will exist in the 3G system in a manner that will allow the user to move freely in most GSM/GPRS and UMTS networks.
INTERWORKING SOLUTION
In ETSI Project BRAN the need for interworking with 3G systems was foreseen early on.The work in ETSI BRAN resulted in two fundamentally different solutions regarding the level of interworking. The two solutions were termed tight and loose interworking according to the level of integration required between the systems. The tight interworking solution was based on the idea of making use of the WLAN radio interface as a bearer for UMTS with all network control entities in the core network integrated. On the other hand, for loose interworking there was little need to make changes to the WLAN standard. This solution has the benefit of not needing a convergence layer, which is an important factor in development time and so on. Loose interworking was therefore adopted as the preferred solution in both the WLAN and 3GPP communities. With respect to security there are large differences between tight and loose interworking. A tight interworking solution would mandate the full 3GPP security architecture and require the 3GPP protocol stacks and interfaces to be present in the WLAN system. The loose interworking options merely require the 3GPP authentication method to be implemented. To avoid link layer modifications, the authentication protocol is allowed to run at the link layer using Internet protocols --Extensible Authentication Protocol (EAP) and authentication, authorization, and accounting (AAA) -- as transpor mechanisms. The main 3GPP-WLAN interworking architecture is defined in 3GPP TS 23.234; the security architecture is found in 3GPP TS 33.234. Figure 1 gives an overview of the 3GPPWLAN architecture.
SECURITY CONCERNS IN 3G-WLAN INTERWORKING
BASIC REQUIREMENTS AND ASSUMPTIONS
A fundamental requirement in 3GPP has been that 3GPP-WLAN interworking shall not com- promise the UMTS security architecture. Therefore, it is required that the authentication and key distribution be based on the UMTS authentication and key agreement (AKA) procedure.997
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