International Journal of Computer Applications (0975 – 8887) Volume 98 – No.21, July 2014 8 An Efficient Trust Management Technique for Delay Tolerant Network Ranjan Singh Mtech Scholar Department of CSE MANIT, Bhopal, India Meenu Chawla, Ph.D Professor Department of CSE MANIT, Bhopal, India ABSTRACT Delay Tolerant Networks (DTNs) have high end-to-end latency, which is often faces disconnection, and unreliable wireless connections. It does not mean a delay service instead DTNs provides a service where network imposes disruption or delay. It operates in challenged networks with extremely limited resources such as memory size, CPU processing power etc. This paper presents an efficient trust managing mechanism for providing secure environment. The proposed dynamic trust management protocol uses a dynamic threshold updating which overcomes the problems with time changing dynamic characteristics by dynamically updating the criteria in response to changing network conditions. This reduces overheads and increases the efficient use of routing network even in conditions change. Also the dynamic threshold update reduces the false detection probability of the malicious nodes. To show the effectiveness of the proposed system, a detailed simulation in the presence of selfish and malicious nodes is performed with ONE simulator. Finally a comparative analysis of our proposed routing with previous routing protocols is also performed. The results demonstrate that presented algorithm deals effectively with selfish behavior with providing significant gain on effective delivery ratio in trade off with message overhead and delay. Keywords Delay Tolerant Networks (DTN), Selfish Attack, Network Security, Trust Management. 1. INTRODUCTION Wireless Delay Tolerant Network (DTNs) [1] is a new Networks class which is characterized by a long message delay and lack of a fully connected path between the source and the target nodes. As a result, the use of mobile nodes acting as a buffer between the one to other end and behave as a store and forward approach. The message moves to a new node when it appears in the range, similarly the messages reach their destinations. The message sending is an opportunistic procedure because the messages are sent in an opportunistic way. Because of its characteristics wide range of useful applications have been developed for DTNs and enable a new class of networking applications in the wireless network interface which increases popularity of mobile devices. DTNs can be used for developing low-cost internet services on remote area moreover it can be used for vehicle DTNs for local advertising, location-based information collection such as traffic reports and parking information. However, the practical DTNs implementation is questionable because its characteristics making them vulnerable to serious security threats. In the system every node predicted that intermediate nodes (or vehicles) are relaying the message properly. However malicious node not carries the message properly in the network which causes multi-hop communications to fail and detection of their presence may be hard. DTNs relay carriers sharing which is the essential requirement, but this cannot be guarantee because selfish nodes can avoid participating for other messages. On other hand malicious node creates the black hole which carries out attacks by deliberately dropping messages. Overcome these attacks is a real challenge due to the connectivity and distributed nature of DTNs. DTN are resource constrained in nature to save its own resources and nodes may develop selfish behavior. In which its drop the packet of other nodes to maximize its own credit or benefits. Such nodes increase the message drop probability and reduce the message delivery rate. In this paper, we propose a dynamic trust based approach to protect network from black hole and selfish attacks. The rest of the paper is organized as follows: the second section provides a brief discussion of the most recent relative literatures of DTNs and the system model is defined in third section. The fourth section explains the proposed algorithm and the simulated results and the fifth section explain about conclusion and future work on the basis of the simulation results presented in fourth section. 2. LITERATURE REVIEW Since the security in the DTN has already an open issue hence this section presents a brief review of some of the recent and relevant literatures. E. Bulut [2] presented a study on DTNs in presence of malicious nodes (also known as compromised DTNs). The literature analyzes the effects of malicious nodes presence on routing in compromised DTNs. They also proposed a two period routing to achieving the required delivery ratio with limited packet lifetime in presence of malicious nodes. The variants of social psychology based approach is one of the commonly found and widely applied [3] [4] [11] [12] because of their similarity with structure of the DTNs. These methods works by checking social characteristics like locality, community and relations to decide packet forwarding or consider other characteristics such as selfishness, unwillingness to avoid packet forwarding. Most of the literature shows that these techniques can effectively improve the routing performance of DTN. A combined social psychology and game theory is presented in [3] [8] which utilize the game theory to find the solution and cause of the social misbehaving. A probabilistic technique for nodes misbehavior detection and efficient trust establishment named iTrust is proposed by Haojin Zhu [8]. The iTrust utilizes the Trust Authority (TA) to periodically check the nodes behavior by cost. Trust Authority is small in numbers because it is fixed and little bit costly, so availability of TA probability cannot be guaranteed if network size is large. Another common approach [11] is trust management which works by estimating the trust level of the nodes either by locally or