Privacy-preserving max/min query in two-tiered wireless sensor networks

In a two-tiered wireless sensor network, resource-limited sensor nodes act as the lower layer for sensing data, and resource-rich storage nodes act as the upper layer for storing data and processing queries from the sink. This architecture has been widely adopted because it can save power and storage consumptions for sensors and improve the efficiency of query processing. However, storage nodes may be compromised in a hostile environment and breach privacy of sensor data. Although privacy-preserving range query and Top-k query have been studied, query for maximum or minimum has not been well addressed. In this paper, we propose a privacy-preserving protocol specializing for MAX/MIN query that prevents adversaries from gaining sensitive information from sensor collected data. To preserve privacy, Prefix Membership Verification approach is employed to encode sensor data such that a storage node can correctly process max/min queries over encoded data without knowing their actual values. Detailed theoretical and quantitative results confirm the high efficacy and efficiency of the proposed schemes.