Secure MAX/MIN Queries in Two-Tiered Wireless Sensor Networks

In wireless sensor networks, secure MAX/MIN query processing is a challenging issue, and it is useful in fields, where security is necessary. In this paper, we propose a secure MAX/MIN query processing method in two-tiered wireless sensor networks. To the best of our knowledge, it is the first work that can achieve data privacy protection and query result integrity verification simultaneously. Three schemes, naïve secure MAX/MIN query (NSMQ), complicated secure MAX/MIN query (CSMQ), and OSMQ, are designed to achieve secure MAX/MIN queries. In NSMQ, we present an intuitive and baseline solution that makes the master nodes return all the ciphertext as the query result. However, it may incur high query communication cost. To address this limitation, a CSMQ scheme is designed, which introduces the comparable factors (c-factors) based on 0–1 encoding verification to find the accurate encrypted query result from the stored ciphertext of the master nodes even when their real values are unknown. Then, a broadcasting method is introduced to generate minor-node-sets as the proofs for verifying the integrity of the query results. CSMQ can significantly reduce the query communication cost, but its in-cell communication cost is high because of the extra data submission and broadcasting. To balance the in-cell and query communication cost, OSMQ, as an optimized version of CSMQ, is proposed to address the minor-node-set compression and random c-factor selection. The proposed schemes are built upon symmetric encryption and hash-based message authentication coding primitives. OSMQ can prevent compromised master nodes from obtaining the plaintext of private data and force them to return integrity-satisfying query results to avoid being detected. Extensive theoretical and experimental studies have been conducted to demonstrate the efficacy and efficiency of the proposed schemes.