Privacy-preserving and secure top-k query in two-tier wireless sensor network

In two-tier wireless sensor networks, resource-rich storage nodes at the upper tier collect sensing data from resource-poor sensor nodes at the low tier, and then answer queries from the user. Sensor nodes perform sensing task and submit sensing data in one time-slot to the nearest storage node while storage nodes answer and process the query from the network owner. However the storage nodes confront serious security concerns. Storage nodes may be compromised and leak the sensitive data as well as returning fake query result. Therefore, it is important to protect the privacy and verify the query results. In this paper, we define and solve the practical and challenging problem of privacy-preserving and verifiable top-k query processing performed on the time-slot sensing data set in two-tier sensor network, and establish a set of privacy and correctness requirements for such a secure top-k query scheme to become a reality. We propose the basic PriSecTopk scheme by using order-preserving encryption, and then improve it step by step to achieve various privacy requirements as well as the correctness requirements in three levels of threat models. Theoretical analysis and experiment on the real-world data set successfully validate the efficacy and efficiency of the proposed schemes.