Towards Secure and Self-stabilizing Sensor Network Services for Civil Security

Licentiatavhandling, 2011

Wireless sensor networks, consisting of a vast number of small sensor nodes that can monitor large areas, are a promising field with many possible applications in many different application areas. In civil security settings, e.g., they can be of great help by monitoring things like disaster areas, restricted areas, crowds and structural integrity. The sensor nodes are deployed in an area that is to be monitored in some way. Typically the nodes do not have any preexisting information about network topology and instead communicate wirelessly to organize the network. Sensor nodes are often very limited in computing power, memory and battery life. In addition the traffic patterns are generally different than for other types of networks. Therefore, algorithms often need to be tailor-made for sensor networks. Furthermore, for networks that consists of a very large amount of nodes, algorithms have to scale well. Security and fault tolerance is of high importance for many sensor network applications and for civil security in particular. The sensor network application needs to remain functioning even when nodes fails or are attacked in different ways. Sensor nodes often reside in harsh environments that can destroy them, during or after deployment. One potent form of fault tolerance is Self-stabilization. A self-stabilizing system can recover from an arbitrary state within a finite amount of time. Security in wireless sensor networks is further complicated by the fact that the nodes often are physically available for attackers to destroy, capture or manipulate in other ways. The threat of compromised nodes inside the network that are controlled by an attacker is a concern that needs to be taken into account. High precision synchronized clocks are a fundamental need of many applications and of other services. We present the first secure and self-stabilizing algorithm for sensor networks that is resilient towards against attacks both from the outside and by compromised nodes from the inside. Sensor nodes also needs to organize their own network. A common way is to cluster nodes together into groups. They are used by many applications and other fundamental services. We present a secure and self-stabilizing algorithm for clustering. It uses redundant paths to be resilient against captured nodes in the network.