document: PRIVE : anonymous location-based queries in distributed mobile systems Nowadays , mobile users with global positioning devices canaccess Location Based Services ( LBS ) and query about pointsof interest in their proximity . For such applications to succeed , privacy and confidentiality are essential . Encryptionalone is not adequate ; although it safeguards the systemagainst eavesdroppers , the queries themselves may disclosethe location and identity of the user . Recently , there havebeen proposed centralized architectures based on K-anonymity , which utilize an intermediate anonymizer between themobile users and the LBS . However , the anonymizer mustbe updated continuously with the current locations of allusers . Moreover , the complete knowledge of the entire systemposes a security threat , if the anonymizer is compromised . In this paper we address two issues : ( i ) We show thatexisting approaches may fail to provide spatial anonymityfor some distributions of user locations and describe a noveltechnique which solves this problem . ( ii ) We propose Prive , a decentralized architecture for preserving the anonymityof users issuing spatial queries to LBS . Mobile users self-organizeinto an overlay network with good fault toleranceand load balancing properties . Prive avoids the bottleneckcaused by centralized techniques both in terms of anonymizationand location updates . Moreover , the system state isdistributed in numerous users , rendering Prive resilient toattacks . Extensive experimental studies suggest that Priveis applicable to real-life scenarios with large populations ofmobile users .
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