Network Coding for Delay Tolerant Networks with Byzantine Adversaries

We consider Delay Tolerant mobile adhoc Networks (DTN) with Byzantine nodes and a binary spraying policy. Under such conditions, nefarious packets may propagate and considerably disrupt performance. We use Network Coding (NC) in this context, with a known number of Byzantine nodes. Existing approaches have considered static networks and us ed end-to-end error-correction schemes with fixed rates, or cr yptographic verification of individual packets. Owing to mobility, an adversarial node may have the same throughput to the receiver as the legitimate sender, thus precluding Byzanti ne NC error-correction schemes. Since we consider DTNs, opportu nistic exchanges allow transmission of cryptographic keys from th e source to only a fraction of nodes in a given time. Our protocol marries cryptographic key dissemination and error-correction to ensure message recovery at the receiver. We distribute keys to a sufficiently high proportion of non-Byzantine nodes, refered to as secure nodes, to limit the propagation of nefarious traffic which may have originated from Byzantine nodes or been coded with traffic from such nodes. Given the ensuing limited ability of the adversarial traffic, we are able to perform error-correction at the receiver. For large networks under uniform and stationary mobility model, we present an analysis of the probability of successful recovery with our protocol in terms of parameter s such as proportion of secure nodes, the level of error-corre cting redundancy we provide and the completion time until decoding is possible. We use the technique of Koetter and Kschischang in our error-correction scheme. We provide numerical resultsfor different random and empirically-obtained mobility trace s.