Security in MANETs is always a very big issue. With evolution of wireless prevalence in the last decade, we are witnessing more and more applications moving and adapting to wireless methods to communicate. But as the financial applications approaches the wireless communication the need of security raised basically MANET nodes rely on multi-hop communication, nodes within each other's transmission range can communicate directly through radio channels, whereas, those outside the radio range must rely on intermediate nodes to forward messages towards destination. So if there is no security there is a possibility that big disasters happen. There are many attacks in MANET due to which the legitimacy of a network is compromised. Such as Black Hole Attacks, Worm Hole Attacks, Byzantine Attacks, DoS Attacks. Many approaches have been given to address these security issues like SAODV, Ariadne, ARAN, Sead. In my approach I will use RSA algorithm for authentication purpose and a blacklist to prevent sending data packets to those nodes which are malicious.