This vision of embeddable wireless connectivity has been in development for several years at AT&T Laboratories Cambridge in the context of the Piconet [6] project and is also being pursued, although with emphasis on different aspects, by several other groups including HomeRF [2,4], IrDA [1] (which uses infrared instead of radio) and Bluetooth [5,3]. Everyone including potential users knows that wireless networking is more prone to passive eavesdropping attacks. But it would be highly misleading to take this as the only, or even the main, security concern. In this paper we investigate the security issues of an environment characterized by the presence of many principals acting as network peers in intermittent contact with each other. To base the discussion on a concrete example we shall consider a wireless temperature sensor. Nearby nodes may be authorized to request the current temperature, or to register a \watch" that will cause the thermometer to send out a reading when the temperature enters a septic range.

Mobile and wireless networks are also experiencing significant progress in the form of wireless local area networks (WLANs) [7], satellite-based networks [8], Wireless Local Loops (WLL) [9], mobile Inter- net

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is Bluetooth (www.bluetooth.net), which provides low-cost and short-range radio links for wireless connectivity among computers, printers, and scanners. Since the range is small, it can use the unlicensed ISM band in 2.4GHz.

Wireless local area networks are designed to provide coverage in a small area, such as a building, hallway, park, or office complex by extending or replacing wired LANs (such as Ethernet). The main attraction is the flexibility and mobility supported by a wireless LAN; bandwidth considerations are secondary.

An overlay network consisting of several Universal Access Points (UAPs). These access points choose a wireless network for the user based on availability, QOS-specified, and user-specified choices. A UAP performs protocol and frequency translation, and content adaptation. By using an overlay network, the handoffs are not performed by the user or the device but by the overlay network as the user moves from one UAP to the other. UAP stores user, network, and device information/capabilities and preferences. This architecture will support single billing and single subscription for users as UAPs can keep track of var- ious resources that have been used by a user. Accessing several wireless networks using the Common Access Protocol. This architecture can be used if wireless networks can support one or two stan- dard access protocols, and requires interworking between different networks. One possible way to sup- port this architecture is to use wireless ATM, meaning every wireless network must allow the transmission of ATM cells with additional headers (or WATM cells) requiring changes in the wireless networks.

Mobile and wireless networks represent the next wave of networking because of their value in assisting an emerging mobile labor force in a growing information-oriented society. However, mobile and wireless networks also present many challenges to application, hardware, software, and network designers and implementers. During the past five years, research has focused on methodically alleviating the limitations of wireless and mobile environment. For example, several optimizations have been introduced to improve the performance of TCP/IP to make it work in slow, failure-prone, and limited bandwidth wireless networks. in addition, proxy servers have been used to improve the performance of application-specific programs (Web browsers, file systems, database servers, and so forth) and mobile users. Over the next five years, research on enabling architectures

queries, mobile dealings, and mobile workflows are also recognized as important emerging research areas. In the near future, worldwide devices that can access the closest/best quality/cheapest wireless network out of several choices will be urbanized. Wireless net- works will be able to implement a uniform addressing system in which a person has a consistent identifying number or network address that is moveable across all wireless networks. Within two to three years, these networks will compete with “wired” networks for applications with low to medium bandwidth supplies. However, with greater than before frequency allocations, advances in semiconductor technology, and more efficient coding of information over wireless channels, mobile and wireless networks will become the net- works of choice for the majority users and applications.

Wireless networks not only enable more efficient, scalable, and reliable wireless services but also provides wider variety of services. These opportunities come with a need for rethinking our security, privacy, architect and billing technologies have been used for previous generations. We believe, however, that future research will overcome these challenges and integrate newly developed services to new generation networks making them available to everyone, anytime and everywhere.

2. Home RF Working Group. http://www.homerf.org/. ACM Mobile Computing and Communications Review, 2(4):38{45, October 1998. 4. Kevin J. Negus, John Waters, Jean Tourrilhes, Chris Romans, Jim Lansford, and Stephen Hui. HomeRF and SWAP: Wireless networking for the connected home. ACM Mobile Computing and Communications Review, 2(4):28{37, October 1998. 5. Bluetooth SIG. http://www.bluetooth.com/ 6. Frazer Bennett, David Clarke, Joseph B. Evans, Andy Hopper, Alan Jones, and David Leask. Piconet: Embedded mobile networking. IEEE Personal Communic- ations, 4(5):8{15, October 1997. 7. LaMaire, R.O., Krishna, A., and Bhagwat, P. Wireless LAN and mobile networking: Standards and future directions. IEEE Communications Magazine (Aug. 1996). 8. Miller, B. Satellites free the mobile phone. IEEE Spectrum (Mar. 1998). 9. Noerpel, A.R., and Lin, Y.-B. Wireless Local Loop: Architecture, technolo- gies, and services. IEEE Personal Communications Magazine (June 1998). 10. Perkins, C.E. Mobile IP. IEEE Communications Magazine (May 1997). 11. Raychaudhuri, D. and Wilson, N.D. ATM-based transport architec- ture for multiservices wireless personal communication networks. IEEE Journal on Selected Areas in Communications (Oct. 1994). 12. Varshney, U. Supporting mobile computing using wireless ATM. IEEE Computer (Jan. 1997).