An autonomous collection of mobile nodes communicating with each other via wireless links either directly or indirectly or relying on other nodes forms the mobile adhoc network (MANET). The routing protocols in MANET are designed based on the assumption that all the participating nodes co-operate. Due to certain issues like open structure and limited energy supply, the nodes sometimes misbehave and act in a selfish manner. 2ACK scheme serves as an add-on technique on few routing protocols (e.g. DSR) to detect such misbehaviour and to mitigate their adverse effect. The major limitation of this 2ACK scheme is additional routing overhead due to authenticated 2ACK packets. Thus, this dissertation work focuses on reducing the routing overhead and end-to-end delay by modifying the authentication mechanism in existing 2ACK scheme. Analytical and simulation results have been presented for evaluating the performance of the work done.