Wireless sensor networking remains one of the most exciting and challenging research domains of our time. As technology progresses, so do the capabilities of sensor networks. Limited only by what can be technologically sensed, it is envisaged that wireless sensor networks will play an important part in our daily lives in the foreseeable future. Privy to many types of sensitive information, both sensed and disseminated, there is a critical need for security in a number of applications related to this technology. Resulting from the continuous debate over the most effective means of securing wireless sensor networks, this paper considers a number of the security architectures employed, and proposed, to date, with this goal in sight. They are presented such that the various characteristics of each protocol are easily identifiable to potential network designers, allowing a more informed decision to be made when implementing a security protocol for their intended application. Authentication ...