This paper considers reliable communication in presence of Byzantine faulty nodes, using multiple node-disjoint routes. To tolerate f Byzantine faults, at least 2f + 1 node-disjoint paths are needed between a source and destination node pair. However, often the faulty nodes' misbehavior manifests itself as a "disagreement" between information provided by the faulty node and its neighbors. This disagreement can be captured in the form of a conflict graph. Even though the conflict graph does not always allow us to identify faulty nodes precisely, we show that it can still be used to reduce the number of paths necessary for reliable communication (to smaller than 2f+1). We consider two strategies for using the node-disjoint paths for reliable delivery of messages: replication and coding across different paths. For each strategy, we propose iPath, a scheme to identify the optimal set of paths that needs to be used to achieve reliable communication for a given conflict graph.

Preserving source location privacy in wireless sensor networks can be critical for several practical applications. Existing solutions proposed specifically for sensor networks rely on a combination of dynamic routing and dummy traffic to hide real event messages. While some privacy protection guarantees can be given, these solutions also tend to be expensive due to fake transmissions and non-shortest path routing overheads. In this paper, we propose a novel idea, of using a combination of directional antennas, transmit power control and information compression to provide lightweight and energy-efficient source location privacy. We discuss the adversary model extensively and then carefully layout characteristics of a realistic adversary. We show how use of directional antennas makes eavesdropping more costly for a realistic adversary and establish relationships between probability of compromise of location privacy, characteristics of directional antennas and size of the adversary's eavesdropping network. Finally, we show how a simple information compression measure can greatly reduce message latency and prolong battery life by conserving energy. Results of extensive simulations in NS2, with our realistic directional antenna add-on, show that compared to existing solutions, we can achieve comparable privacy protection, better message latency, delivery ratio and many orders of magnitude improvement in energy consumption.

In this paper, we make a case for using watchdogs to protect against misbehavior in dense wireless networks. We introduce “Generalized Watchdogs” and identify when and how watchdogs can be necessary and sufficient against misbehavior. We study feasibility of watchdog approach and show that the order of capacity bounds is preserved asymptotically even with watchdogs. We use generalized watchdogs to design protocols to improve both security and performance of TCP over wireless networks such that the application at the destination never accepts a corrupted packet and we achieve this without modifying TCP. We show that a strict dependence on availability and success of watchdogs can lead to “watchdog induced losses” and establish their effects on TCP throughput. We then propose solutions to deal with these losses and make watchdogs intelligent so they can tune the overheads incurred. With hop-by-hop verification of packet correctness, we ensure that tampered packets are not forwarded in the network and thus save potential wastage of network resources. We use NS-2 simulations of both controlled as well as realistic network scenarios, to show that watchdogs can provide simple, lightweight and reliable means of misbehavior detection, tolerance and most importantly “deterrence” while saving costs of security infrastructure. With a combination of intelligent watchdogs and source coding, and by leveraging route adaptation, our scheme achieves twice the throughput of a cryptographic alternative and that too in presence of as high as 30% packet tampering.