NNFDA: A Digest-Based Integrity Verification Scheme for Enhancing Secure Queries in Loss-Tolerant TMWSNs

Tiered Mobile Wireless Sensor Networks (TMWSNs), consisting of mobile sensor nodes and storage nodes, are widely used in various fields due to their scalability, energy efficiency, and flexibility. Most existing secure query algorithms assume that data packets generated by sensor nodes can always be delivered to storage nodes. This assumption does not hold in practice, where packets may be lost due to attacks or adverse communication conditions. This paper proposes a loss-tolerant wireless network model for TMWSNs and a novel threat model tailored to this scenario, in which packet-dropping attacks compromise the integrity of query results. To counter these attacks, we present a baseline integrity verification algorithm, the Neighbor Node-Forwarding Digest Algorithm (NNFDA). Each sensor generates a digest of its data and forwards it to neighboring nodes. These digests are then transmitted to storage nodes together with the neighbors’ data, thereby establishing a chained relationship among sensor data. The base station verifies query results using this relationship. The baseline algorithm, however, causes high communication overhead. To reduce this cost, we propose an improved version, NNFDA-BM (NNFDA with Bitmap), which optimizes digest generation and transmission. Experimental results show that NNFDA-BM verifies query result integrity effectively while achieving a significant reduction in communication overhead compared with the baseline algorithm.