Private location-based information retrieval through user collaboration

Privacy and security are paramount in the proper deployment of location-based services (LBSs). We present a novel protocol based on user collaboration to privately retrieve location-based information from an LBS provider. Our approach does not assume that users or providers can be completely trusted with regard to privacy, and does not rely on a trusted third party. In addition, user queries, containing accurate locations, remain unchanged, and the collaborative protocol does not impose any special requirements on the query–response function of the LBS. Our protocol is analyzed in terms of privacy, network traffic, and processing overhead. We define the concept of guaranteed privacy breach probability, and we show that our proposal provides exponential scalability in that probability, at the expense of a linear relative network cost.