| Wireless sensor networks have received a lot of attention recently due to its wide applications. Accurate and synchronized time is crucial in many sensor network applications. A number of time synchronization schemes have been proposed recently to address the resource constraints in sensor networks. However, all these techniques cannot survive malicious attacks in hostile environments.; This dissertation includes three techniques to achieve secure time synchronization in different scopes of sensor networks. First, we develop a secure single-hop pair-wise time synchronization technique that provides time difference between two neighbor nodes using hardware-assisted, authenticated medium access control (MAC) layer timestamping. This technique can effectively defeat external attacks that attempt to mislead single-hop pair-wise time synchronization.; Second, we propose a fault-tolerant cluster-wise time synchronization scheme to provide a common clock among a cluster of nodes, where the nodes in the cluster can communicate through broadcast. This scheme guarantees an upper bound of time difference between normal nodes in a cluster, provided that the malicious nodes are no more than one third of the cluster. Unlike the traditional fault-tolerant time synchronization approaches, the proposed technique does not introduce collisions between synchronization messages, nor does it require costly digital signatures.; Third, we propose two secure and resilient global time synchronization schemes: level-based time synchronization and diffusion-based time synchronization. The basic idea of both schemes is to provide redundant ways for one node to synchronize its clock with another far-away node, so that it can tolerate partially missing or false synchronization information provided by compromised nodes. The level-based scheme builds a level hierarchy in the sensor network, and then synchronizes the whole network level by level. The diffusion-based scheme allows each node to diffuse its clock to its neighbor nodes after it has been synchronized. Both schemes are secure against external attacks and resilient against compromised nodes. We implement a secure and resilient global time synchronization protocol, TinySeRSync, on MICAz motes running TinyOS. The experimental results indicate that TinySeRSync is a practical system for secure and resilient global time synchronization in wireless sensor networks. |
