EVTQ: An Efficient Verifiable Top-k Query Processing in Two-Tiered Wireless Sensor Networks

We consider a capable and scalable network model named two-tiered sensor network which consists of regular resource-limited sensor nodes and powerful storage nodes with abundant resources. In such architecture, storage nodes are on charge of storing data collected and submitted by sensor nodes as well as processing queries from the base station. Owing to the importance role that storage nodes play, they are more vulnerable and attractive to adversaries in a hostile environment. A compromised storage node may inject fake data into and/or omit qualified data from its returned responses, which make the base station not able to obtain authentic and/or complete results. This paper proposes EVTQ, a novel and efficient verifiable top-k query processing which is capable of verifying the authentication and completeness of query result. To achieve such security features, sensor nodes are settled to submit their collected data items together with corresponding codes which embed ordered and adjacent relationships of the collect data items by a hashed message authentication coding function. Thus any attack that leads to unauthentic and incomplete query result will be detected. According to this basic idea, the data submission and query processing protocols are proposed to describe the details of EVTQ. Moreover, a hash based optimization is presented to save more communication cost. The simulation result shows that EVTQ is more efficient than the existing work in communication cost.