Unlike fixed networks, mobile ad-hoc networks have diverse characteristics, such as dynamic topologies, bandwidth-constrained links, energy-constrained operation, limited physical security, etc. Due to these characteristics their security requirements are different from those of fixed networks. This paper presents a method of authenticating the nodes in the ad-hoc network and securely transmitting information in consideration of the characteristics of the mobile ad hoc network. To this end, this paper proposes a method of combining asymmetric and symmetric cryptography to enhance the efficiency of secret key management for authentication and secure channel establishment. In particular, this paper proposes a method that introduces the concept of Hamming Distance to share the secret keys between the nodes. According to this proposal, secure communication between the nodes is possible when one node manages only log 2N secret keys.