Protocols for mitigating blackhole attacks in delay tolerant networks

High node mobility and infrequent connectivity in delay tolerant networks (DTNs) makes it challenging to implement traditional security algorithms for detecting malicious nodes. In DTN, most of the routing algorithms are based on the announcement of routing metrics like probability of delivery, contact strength or social group strength by the nodes in contact. Blackhole in DTN exploits these characteristics of routing protocols and either announces a high value of these metrics or tries to attain a high value for them by following fast, repeated movement patterns. Dynamic social grouping (DSG) based routing algorithm shows that social behavior of nodes helps to make better forwarding decisions and to achieve highest message delivery ratio amongst other existing routing algorithms. We examine the impact of blackholes, intermittent blackholes and tailgating attack on DSG. We propose a suit of three solutions. Our first solution detects blackholes and tailgating malicious nodes in the network, however, is not suitable for intermittent blackholes. Second solution handles intermittent blackholes and performs well when the nodes are well connected. The third and final solution handles intermittent blackholes in sparsely connected as well as in well-connected networks. In all proposed solutions, blackholes are not able to degrade the performance of the protocols by changing their geographical locations. We demonstrate through simulation that our protocols improve upon the message delivery ratio over the existing solutions. An appropriate protocol from the suit may be used depending upon an application.