Wireless Sensor Networks (WSNs) gain popularity these days. WSNs have been one of key technologies for the future with broad applications from the military to everyday life. There are two kinds of WSNs model models with sensors for sensing data and a server for receiving and processing queries from users; and models with special additional nodes, their common names are storage nodes, between the sensors and the sink. Among the latter type, a two-tiered model has been widely adopted because of its storage and energy saving benefits for weak sensors, as proved by the advent of commercial storage node products such as Stargate and RISE. In this paper, we consider two-tiered WSNs model that consists of sensor nodes receiving data from the environment and transferred to storage nodes, the queries from the server will be done through these storage nodes. In this model, the problem is how to ensure privacy of data at the storage nodes, which is mostly located in the hostile area. Data encryption is the popular solution to make the unreadable for storage node. However, if the server needs data in the range, then storage node must read the data to reply server's query. In order to solve this problem, we proposed to use a d-disjunct matrix, an order-preserving function and a permutation function that encode data of each sensor. An order-preserving function is used to query. Simultaneously, the permutation function and d-disjunct matrix will be used to encrypt data and determine the exact frequency of any value. With this approach, we have proved that our solution guarantees to preserve data-privacy while allowing the range query efficiently. In particular, it just takes less than 60 seconds when we encrypt or query less than 200000 values.
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