In a sensor network environment, elements such as message rate, message size, mote frequency, and message routing can reveal transactional data—that is, information about the sensors deployed, frequency of events monitored, network topology, parties deploying the network, and location of subjects and objects moving through the networked space. Whereas the confidentiality of network communications content is secured through encryption and authentication techniques, the ability of network outsiders and insiders to observe transactional data can also compromise network confidentiality. Four types of transactional data are typically observable in sensor networks. Measures to limit the availability and utility of transactional data are essential to preserving confidentiality in sensor networks.