Delay tolerant networks (DTNs) are resource-constrained networks where messages are relayed in a store-carry-forward fashion. In most routing protocols of DTNs, each node is required to honestly relay messages. However, some nodes may violate this principle, and relay messages in a greedy way in order to maximize their own benefit, such as to get more transmission opportunities and more rewards, and to save their own resources. This greedy behavior breaks the routing fairness and decreases the m