A Co-operative Approach to Thwart Selfish and Black-Hole Attacks in DTN for Post Disaster Scenario

A Delay Tolerant Network (DTN) is prone to security threats, especially the Selfish and Black-hole attacks. In this work, we have taken up these two security issues in a DTN based on an architecture suitable for Post disaster scenario, where mobile nodes move around a fixed destination and communicate messages to it. A co-operative scheme is presented to reduce the harmful effects of these malicious nodes in the network. The cooperation is obtained from the neighbouring nodes. The malicious behavior of a node is examined at the time of sending messages to that node by inquiring other neighbouring nodes about the past performances of that node. Simple parameters, such as total number of sent and received messages to and from other nodes and the elapsed time since the network is active, are used for arriving at the decision of forwarding messages to that node. The node whose malicious behavior is being tested is not involved in the whole process as it may manipulate information to pose as a valid node. By the cooperation of other neighbouring nodes, a combined faith value (CFV) is calculated. If this value satisfies a pre-defined threshold condition, then the node is treated as valid for that moment. The process is performed every time a node wants to transmit a message to another node. Also, the calculated CFV is multicast in the neighbourhood for updating. The scheme has been tested on the Spray and Wait (S&W) DTN routing protocol with mobile nodes and fixed destination type architecture to prove its effectiveness. It is found to avoid malicious nodes and increase the trustiness of the network and data communication.