SUMMARY
A Wireless Sensor Network (WSN) is composed of a large number of sensor nodes deployed over a geographical area. Each node is a low-power device that integrates computing, wireless communication, and sensing abilities. Many applications that make use of sensor networks require secure communication. Designing an efficient key establishment scheme is of great importance to the data security in Wireless Sensor Networks. The traditional cryptographic techniques are impractical in Wireless Sensor Networks because of associated high energy and computational overheads.This algorithm supports the establishment of three types of keys for each sensor node, an individual key shared with the base station, a pair wise key shared with neighbor sensor node, and a group key that is shared by all the nodes in the network. The algorithm used for establishing and updating these keys are energy efficient and minimizes the involvement of the base station. Polynomial function is used in the study to calculate the keys during initialization, membership change and key compromise. Periodically the key will be updated. To overcome the problem of energy insufficiency and memory storage and to provide adequate security, the energy efficient scheme is proposed. It works well in undefined deployment environment. Unauthorized nodes should not be allowed to establish communication with network nodes. This scheme when compared with other existing schemes has a very low overhead in computation, communication and storage.