A Defense Mechanism for EOLSR against DOS Attacks in Ad hoc Networks Using Trust Based System

Abstract

The process of routing in MANET (Mobile ad hoc network) requires a trust based environment and therefore security is one of the major concern. A backbone network in a MANET is difficult when it is implemented for a specific application. A security based environment is one of the most critical issues in a MANET because it is mostly involved with sensitive and secret information. This work deals with a specific type of denial-of-service (DOS) attack called node isolation attack and thus analyze the vulnerabilities of a pro-active routing protocol called optimized link state routing (OLSR). Based on this analysis, this work proposes a mechanism called enhanced OLSR (EOLSR) protocol which is a trust based technique to secure the OLSR nodes against the attack. According to the proposed technique, isolation can be detected by the hello packets it sends. Verification is done through this, whether a node is advertising correct topology information or not thus leading to detection of the isolation node that perform the DOS attack. Enhanced OLSR is further improved using the trust based system called Trustbased OLSR (TOLSR). Once the node is detected as attacker using EOLSR, its trust value is reduced to half of its initial value. Hence in future, selection of attacker as MPR node is prevented since all the nodes will select only high trust node as MPR node. The concept of ensuring security to the network does not involve much computational complexity and therefore, the proposed scheme is a light weight technique.