Byzantine Fault Tolerance of Inverse de Bruijn Overlay Networks for Secure P2P Routing

Byzantine faults in a peer-to-peer (P2P) system are resulted from adversarial and inconsistent peer behaviors. Malicious peers can disrupt the routing functions in peer joining and lookup services. Byzantine attackers may collude with each other to paralyze the entire P2P network operations. We discover a new class of DHT-based overlay networks, called inverse de Bruijn (IDB) graph, to enable multi-path P2P routing. The IDB overlays provide multiple entry points and multiple routes between node pair. These features enable secure routing services in O(logk n) time with O(k logkn) lookup messages and O(klogk n) joining messages, where the graph index k ≥ 2 and the full overlay has n=k nodes. For large index k >> 2, the IDB overlays handle random and Byzantine faults effectively, far beyond the capability of Chord or CAN. The IDB overlays establish a Byzantine fault tolerance (BFT) framework, by which secure P2P routing is guaranteed by using multiple routes to bypass faulty route. New BFT routing algorithms are developed for secure joining and lookup operations. Consequently, fault tolerance is achieved by majority vote on data returned from multiple routes. The paper presents graph-theoretic properties of sparse IDB overlay networks and the protocols needed to establish the BFT. Experimental results are reported on simulated IDB and Chord overlays. Both theoretical and experimental results support the claimed BFT advantages. The performance gain is obtained with small increase in messaging overhead. In summary, the IDB overlays are ideal to cope with peer collusions or Byzantine attacks in DHT-based P2P systems.