In recent years, Mobile Ad-hoc Networks have received an immense attention in both industry and academia as they provide dynamic networking services. Such networks are rapidly deployable in the future, so secure wireless environment will be obligatory. In mobile ad hoc networks, due to unreliable wireless media, lack of fixed infrastructure and host mobility, providing secure communications is a big challenge. Because a temporary device recurrently joins or leaves a network, the authentication and security technology should be equipped for the malicious devices used in third-party attacks. Usually, symmetric and asymmetric cryptographic techniques are used for secure communications in wired and wireless networks but they have their advantages and disadvantages. In fact, any cryptographic means is ineffective if its key management is fragile.