Browsing by Author "KALNIS, Panos"

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    Preserving Anonymity in Location Based Services
    (2006-06-12) KALNIS, Panos; GHINITA, Gabriel; MOURATIDIS, Kyriakos; PAPADIAS, Dimitris
    The increasing trend of embedding positioning capabilities (e.g., GPS) in mobile devices facilitates the widespread use of Location Based Services. For such applications to succeed, the privacy and confidentiality issues are of paramount importance. Existing techniques, like encryption, safeguard the communication channel from eavesdroppers. Nevertheless, the queries themselves may disclose the physical location, identity and habits of the user. In this paper, we present a framework for preserving the anonymity of users issuing spatial queries to Location Based Services. We propose transformations based on the well-established K-anonymity technique to compute exact answers for Range and Nearest Neighbor queries, without revealing sensitive information about the user. Our methods optimize the entire process of anonymizing the requests and processing the transformed spatial queries. Extensive experimental studies suggest that our methods are applicable to real-life scenarios with numerous mobile users.
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    PRIVE: Anonymous Location-Based Queries in Distributed Mobile Systems
    (2006-07-31T08:52:08Z) GHINITA, Gabriel; KALNIS, Panos; SKIADOPOULOS, Spiros
    Nowadays, mobile users with positioning devices can access Location Based Services (LBS) and query about points of interest in their proximity. For such applications to succeed, privacy and confidentiality are essential. Encryption alone is not adequate; although it safeguards the system against eavesdroppers, the queries themselves may disclose the location and identity of the user. Recently, there have been proposed centralized architectures based on K-anonymity, which utilize an intermediate anonymizer between the mobile users and the LBS. However, the anonymizer must be updated continuously with the current locations of all users. Moreover, the complete knowledge of the entire system poses a security threat if the anonymizer is compromised. In this paper we address two issues: (i) We show that existing approaches may fail to provide spatial anonymity for some distributions of user locations and describe a novel technique which solves this problem. (ii) We propose PRIVE, a decentralized architecture for preserving the anonymity of users issuing spatial queries to LBSs. Mobile users self-organize into an overlay network with good fault tolerance and load balancing properties. PRIVE avoids the bottleneck caused by centralized techniques both in terms of anonymization and location updates. Moreover, the state is distributed in numerous users, rendering the system resilient to attacks. Extensive experimental studies suggest that PRIVE is applicable to real-life scenarios with large populations of mobile users.