Wireless Sensor Networks (WSN) is an emerging technology. Now-a-days, sensor networks have great potential to be employed in mission critical situations like battlefields but also in more everyday security and commercial applications. Such as building and traffic surveillance, habitat monitoring and smart homes etc. One of the major challenges wireless sensor networks face today is security. Confidentiality, integrity, and authentication services are critical to preventing an adversary from compromising the security of a WSN. The wireless communication technology also acquires various types of security threats.