Defense of a variant of rushing attack on ExOR

ExOR, which makes the best use of every broadcast and chooses the next hop after the transmission for that hop, is an opportunistic routing protocol in Wireless Mesh Network (WMN). While effectively increasing the throughput of the network, ExOR doesn´t take any security mechanism into account. Since ExOR attempts to schedule the transmission by the cooperation of each node, the scheduling mechanism of ExOR is easily damaged by attackers. In this paper, we first introduce a variant of rushing attack, which targets on the scheduling mechanism of ExOR. The attacker violates the scheduling mechanism and forwards the fragment regardless of higher priority nodes´ sending, which results in the wrong setting of other nodes´ forwarding timer. And then we propose the anti-rushing mechanism, a defense against the variant of rushing attack for ExOR. This mechanism uses one-way hash chain for authentication and requires each node should send the packets with the last sender´s hash that its forwarding timer setting based on to prove its timer setting is not malicious. Our mechanism is proved to be effective through a series of experiments.