Wireless Sensor Networks (WSNs) are being deployed widely in hazardous and hostile environments for avariety of civil and military applications. They pose unique security challenges because of their inherent limitations in communication and computing power. This talk covers some of the key security challenges of WSNs. Among those security challenges, we focus more on the key management problem and present some new and some classical protocols for key management. We also discuss our experience with the analysis of a popular protocol for key management. Our analysis uses an automatic tool for protocol verification.