SET: Secure and Efficient Top-k Query in Two-Tiered Wireless Sensor Networks

Top-k query is one of important queries in wireless sensor networks (WSNs). It provides the k highest or lowest data collected in the entire network. Due to abundant resources and high efficiency, many future large-scale WSNs are expected to follow a two-tiered architecture with resource-rich master nodes. However, the sensor network is unattended and insecure. Since master nodes store data collected by sensor nodes and respond to queries issued by users, they are attractive to adversaries. It is challenging to process top-k query while protecting sensitive data from adversaries. To address this problem, we propose SET, a framework for secure and efficient top-k query in two-tiered WSNs. A renormalized arithmetic coding is designed to enable each master node to obtain exact top-k result without knowing actual data. Besides, a verification scheme is presented to allow the sink to detect compromised master nodes. Finally, theoretical analysis and experimental results confirm the efficiency, accuracy and security of our proposal.