As described above in the security work flow, the second authentication phase is to apply and issue a proxy credential. Normally, the master node and the CA server are distributed at different locations and connected via a public network, which is insecure to transmit sensitive information. On the other hand, a proxy credential functions as the identity of the user instance that is given by the CA server. It is used to authenticate the master node with the related user instance by slave nodes, so that the user instance can access or use the resources of G-Hadoop. Therefore, a secure and trustful com- munication between the master node and the CA is required. In this work, the SSL protocol is chosen to guarantee the security of the communication. According to the features of the SSL protocol, SSL has the ability to avoid the man-in-the- middle (MITM) attack, version rollback attack, delay attack, and replay attack. In addition, it provides an extension solution of client-authenticated handshaking, which performs the authentication of both communication parties before the secure connection is set up. This feature meets the requirement of our security framework, where the master node, which acts as the client in the SSL connection, is authenticated by the CA server and a fraudulent party as the fake master node is refused by the CA server.