A mobile ad hoc network is part of wireless networks which is formed by collection of two or more nodes moving in an arbitrary manner. The nodes are self organizing, adaptive, infrastructure less and has dynamic topology. Hence due to high mobility and multipath propagation network is vulnerable to attacks. There are many types of MANET like VANET (Vehicular Ad hoc Network), SPANs (Smart Phone Ad hoc Networks), iMANET (Internet based Mobile Ad hoc Network), Tactical MANET. There are various attacks that can be possible on MANET like Denial of Service attack, Black hole attack, Wormhole attack, Sybil attack etc which can disturb the communication between the nodes. So today's requirement is to provide secure and authentic communication in MANET. For small network security is not a big issue but for large or complex network security should be provided in large extent. To provide security for complex networks in the network using a technique Seniority Based Pretty Good Privacy (SBPGP) is used.