Wireless sensor networks face security challenges including key establishment, secrecy, authentication, privacy, and robustness to denial-of-service attacks. The document outlines these security issues and discusses the current state of research in sensor network security. It also covers required security services and future research challenges, such as secure routing and protecting networks from node capture. Additionally, the document notes that most current wireless sensor networks measure physical phenomena like temperature or location but that wireless multimedia sensor networks could support applications with higher bandwidth demands and less tolerance for delay.