Secure Routing in DSR to Mitigate Black Hole Attack Ashutosh Bhardwaj Department of Computer Science and Engineering Indian Institute of Technology Roorkee Roorkee - 247667, Uttarakhand, India ashu9pec@iitr.ac.in Abstract— Mobile adhoc networks (MANETs) consist of mobile nodes with no fixed infrastructure. Dynamic Source Routing (DSR) which is on-demand routing protocol is a widely accepted mobile adhoc network routing protocol used to provide connectivity to mobile nodes. However, DSR and other on- demand routing protocols are vulnerable to different types of security attacks and black hole attack is one of them. In black hole attack, malicious node sends a fake route reply in response of route request to source node claiming for an optimal route to the destination. Thus, node which starts route discovery process establishes a path through malicious node and starts sending data packet on this route. Malicious node drops the data packet which reduces packet delivery ratio. To secure DSR, we propose a scheme which confirms the authenticity of route with the help of verification packet. This packet is generated by first intermediate hop in the route of route reply. Simulation results show improvement in packet delivery ratio and throughput. Keywords —MANET, DSR, Routing, Black hole, Security I. INT RODUCT ION A mobile adhoc network contain number of mobile nodes, which plays an important role in routing. Mobile nodes which are in same radio communication range communicate directly otherwise requires cooperation of other nodes and perform multi-hop communication [1]. In multi-hop communication, nodes communicate without infrastructure and provide connectivity by forwarding packet to neighbor. For this connectivity node uses routing protocol. Network topology in MANET change frequently and changes are distributed among nodes. Nodes may join or leave network and are required to work with collaboration due to absence of central control in network operation. A node acts as host and router simultaneously. Routing decision has great importance in security concerns. The network can be broken if routing is misdirected. The problem is enlarged because routing rely on trust of all nodes that participate in routing. Since nodes in adhoc network are mobile, they are free to move in any direction. Therefore any security solution which takes static value would not be applicable in such dynamically changing topology. In MANET, due to absence of central coordinator, most routing algorithms are based on cooperative participation of all nodes. Thus in this situation we cannot apply centralized solution because malicious node could block or modify traffic by denying cooperation to break cooperative algorithms. Because to absence of central coordinator authentication based on certification authority and public key cryptography may be difficult, therefore nodes are easy to hijack, capture and compromise. Due to such flexibility of mobile nodes, developing a secure routing protocol in MANET is hard as compared to a wired network A Lot of research has been done to overcome the vulnerabilities of security in routing protocols like intrusion detection techniques, authentication techniques [2], [3], [4]. Among various issues in MANET, we focused on secure routing in this paper. There is a possibility of several types of attacks in many on demand routing protocols and black hole attack is one of them. During this attack intermediate node sends fake route information in response of route requests to source node and claiming for optimal route to destination. Thus a source node establishes a route through malicious node and sends data packet through this route. A malicious node drops the data packet which reduces the packet delivery ratio. II. RELATED WORK A. Routing in MANETs Routing in MANETs is different from traditional routing on infrastructure network. Main aim behind routing is to provide efficient route between nodes so that message can be delivered. Routing in mobile adhoc networks is a challenging area because regular change in topology and frequent disconnections are common as nodes moves from one place to another. Routing in MANETs depends upon several features like topology, route selection, initiation of request and specific underlying features. Many routing schemes are present in mobile adhoc network to provide optimal routing which is necessary due to low resource availability. On the basis of time of route discovery, these schemes are divided into proactive routing [5] and reactive routing [6]. In proactive routing, nodes maintain a routing table which contains entries for all possible destinations so that it can be forwarded immediately when required. As a result node experiences a minimum delay. However proactive routing continuously uses fraction of network bandwidth to maintain current routing information. Reactive routing uses lazy technique, where node discovers route to destination only on demand or when requires. Node never store route until required and before sending packet node first apply approach for finding route and consumes less bandwidth as compared to proactive routing but 985 2014 International Conference on Control, Instrumentation, Communication and Computational Technologies (ICCICCT) 978-1-4799-4190-2/14/$31.00 ©2014 IEEE