Positioning and Privacy in Location-Based Services

With the advent of new-generation smart mobile devices such as Apple iPhone and Google gPhone, location positioning by GPS and aGPS (assistedGPS) become a standard function in handheld device specifications. Texas Instruments forecasts that by 2012, 34% of mobile handsets will be shipped with GPS modules. Even in indoor environments, positioning by utilizing signals from the mobile cellular network and the wireless LAN has been intensively studied and its accuracy has been sigLocation positioning by GPS has become a standard function in modern handheld device specifications. Even in indoor environments, positioning by utilizing signals from the mobile cellular network and the wireless LAN has been intensively studied. This chapter starts with some review of the state-of-the-art technologies. Positioning technologies propel the market of location-based services (LBS). They are mobile content services that provide location-related information to users. However, to enjoy these LBS services, the mobile user must explicitly expose his/her accurate location to the service provider, who might abuse such location information or even trade it to unauthorized parties. To protect privacy, traditional approaches require a trusted middleware on which user locations are anonanonymous ymized. This chapter presents two new privacy-preserving approaches without such a middleware. The first is a non-exposure location cloaking protocol where only relative distances are exchanged. The second is a protocol for nearest neighbor search with controlled location exposure.