The Kerberos protocol
The Kerberos protocol is built to protect authentication between the server and the client in an open network.
The main concept behind authentication is that two parties first agree on a password (secret) and then use it to identify and verify their genuineness:
Figure 16.1: Authentication by using a secret
In the preceding example, Dave and server A have a communication link. They often exchange confidential data. To protect this communication, they agree to use a common secret code (1234) to verify their identities before exchanging data. When Dave makes the initial connection, he passes his secret to server A and says Hey! I'm Dave. Then, server A checks the secret to see whether it's true. If it's correct, it identifies him as Dave and allows further communication.
Figure 16.2: Man-in-the-middle attack
Communication between Dave and server A happens in an open network, which means that other systems and users...