A collaborative k-anonymity approach for location privacy in location-based services

Considering the growth of wireless communication and mobile positioning technologies, location-based services (LBSs) have been generating increasing research interest in recent years. One of the critical issues for the deployment of LBS applications is how to reconcile their quality of service with privacy concerns. Location privacy based on k-anonymity is a very common way to hide the real locations of the users from the LBS provider. Several k-anonymity approaches have been proposed in the literature, each with some drawbacks. They need either a trusted third party or the users (or providers) to trust each other in collaborative approaches. In this paper, we propose a collaborative approach that provides k-anonymity in a distributed manner and does not require a trusted third party nor the users (or providers) to trust each other. Furthermore, our approach integrates well with the existing communication infrastructure. A user's location is known to only his/her location provider (e.g., cell phone operator). By using cryptographic schemes, user with the help of location providers determines whether the k-anonymity property is satisfied in a query area or not. We start with a simple scenario where user and location providers are honest-but-curious and then we progressively extend our protocol to deal with scenarios where entities may collude with each other. Moreover, we analyze possible threats and discuss how our proposed approach defends against such threats.