In the past few years, we have seen a rapid increase in important application fields of Mobile ad-hoc networks (MANET). Hence, many industrial and academic researchers have been conducted. Because, these applications are closely related to human beings and their physical environment, the usage of MANET on a large scale depends on whether we can provide proper dependability. Particularly, security is the most important issue in MANET because of the limitation in resources. Management of keys is the most necessary activity for providing security for the network. MANETs have resource limitations. Thus using public-key based solutions is not feasible. Thus, we use symmetric key establishment. In this paper, a key management scheme which is self contained and public is represented. This scheme achieves near zero communication overhead while providing security services. Cryptographic keys in small numbers are inputted at all nodes prior to the deployment in network. Mathematical Combinations of pairs of keys, both public and private is used for better utilization of storage space. This means a combination of more than one key pair is utilized by nodes for the encryption and the decryption of messages. A secure communication algorithm for forwarding the packets in MANET is also proposed.