Worldwide interoperability for Microwave Access (WiMAX) is an emerging wireless technology for the future. With the increasing popularity of Broadband internet, wireless networking market is thriving. Wireless network is not fully secure due to rapid release of new technologies, market competition and lack of physical infrastructure. In the IEEE 802.11 technology, security was added later. In IEEE 802.16, security has been considered as the main issue during the design of the protocol. However, security mechanism of the IEEE 802.16 (WiMAX) still remains a question.