Abstract
Ad hoc networks is a kind of type of the wireless networks that it’s technology is still developing and studied. Its system is build on the distributed network. Every member in the Ad hoc networks works individually without a base station controlling and authenticating constantly. The way of data transformation in Ad hoc networks is to hop through the other member that is between the source member and destination member. Its application nowadays is usually used in the military way, such as the measurement of the battle field. However the application is becoming more various, such as the volcano environment measurement, the creature motion detection, and wireless networks meeting .However, such distributed system is much easier attacked by the adversary than the centralized networks system because of absence of authentication authority during communication process. The type of attack is including DoS attack, and impersonation that already exits in the centralized networks system,in addition to the eavesdrop in the wireless environment. So the security problem of the Ad hoc network is becoming more and more important in the development of such networks technology. We proposed a scheme to modified the Blom scheme that is considered as a public key cryptography system to against the security problem of the Ad hoc networks. Then we compared our scheme with other scheme that present by others in the computational source used and cryptography system broken probability that are the most important considered in Ad hoc networks.