Location-based service providers, which are different companies or organizations, play the role of spatial data maintainers and spatial query processors. In order to handle privacy protected query, providers should implement specific query processors in their databases for different privacy preserving methods, which is infeasible for the diversity of providers and privacy preserving methods. What's more, existing privacy preserving methods address location privacy threatens by revealing only the cloaked area or fake locations to server. It must induce some errors into query results and additional cost for dealing with cloaked spatial regions rather than exact location information. In this paper, we present PPSQP (privacy protected spatial query processor) to avoid the errors for kNN (k-Nearest Neighbors) queries and range queries. A privacy protected kNN query is translated into one common kNN query and one range query without privacy decline and specific processor in the server side. Theory analysis and experimental result present PPSQP achieves location privacy protection with linear cost.
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