• Proxy credential and slave credential: Proxy credentials and slave credentials are used by our security framework to
describe two different certificates. They are issued by the same CA (Certification Authority).
The proxy credential is designed for slave nodes to authenticate the master node, actually the user instances maintained
on the master node. For each user instance a proxy credential is issued. After a user instance is authenticated by a
slave node, a secure communication is established and the proxy credential is not required any more. Therefore, proxy
credentials are designed as one-time-usage and have short life cycle to protect the authentication process from MITM
attacks and replay attacks. A proxy credential contains the following information: the CA identity, the expiration time,
a public key of the master node as well as its life cycle, and a random message that is generated by the CA.
In contrast to a proxy credential, a slave credential has a long life cycle and is owned by a slave node. Slave credentials
are used by the master node to authenticate the slave nodes during the procedure of establishing a communication
channel between the master node and a slave node. A slave credential contains information about the CA identity and
the public key of the corresponding slave node.