This paper describes a secure top-k query processing scheme that is secure under the security model. The data privacy is guaranteed by encryption as well as a careful generation of data indexes. In this paper make to transform a top-k query, to a top-range query and adopt membership testing to test whether an associate pattern should be included in the query result or not. This transformation allows the storage node to find Top-k smallest or biggest data values without using numerical comparison operations, which is a key technique for the scheme to be secure under the security model. In the proposed system, it defines a new type of behavioral patterns for WSNs, termed as associated sensor patterns to capture the true correlation among sensor data. To discover such patterns, it uses to devise a highly compact tree structure, called weight associated sensor pattern tree (WASP-tree) and a mining algorithm that can efficiently discover patterns from sensor database (SD) with a single scan.