Security and authentication are critical in Wireless Sensor Networks (WSNs). These networks are deployed in nasty environment under very less or no human supervision and mostly in unattended areas. Autonomous nature with tiny, resource constrained sensor nodes coupled with wireless nature make them unique and at the same time challengeable. The features are most unique, thus making these networks useful in diverse areas. The tasks assigned to these networks are generally of sensing the values or parameters which humans can't gather or sense.