As mentioned above, G-Hadoop was developed for a computing environment with large-scale distributed multiple clus- ters. The system components, including the CA server and the master node of G-Hadoop, may be distributed over the world and connected via a public network, for example the Internet, where various security threats exist. Hence, one component can trust another only when the authentication process is successfully conducted. However, the CA server has to be trusted by all components of the system. This is the basis condition of using certificates for authentication.