Challenge Handshake Authentication Protocol (CHAP)
Challenge Handshake Authentication uses Point to Point Protocol servers to validate the authenticity of the remote client that is trying to access the network. This form of authentication also makes use of what is called a three way handshake. It does this by periodically validating the user.
For instance, when you initially link to the server you will do so with the point to point protocol as well as supplying for example, a user name.
The system will remember and make note of the user name and only ask for the user name every once in a while. Not every time you link to the network.
This is done by the use of a challenge message sent to the peer from the user. The peer would then send back a value that would include the challenge answer and the secret combination.
The only way the system would allow the user access would be if the values matched, f they match then the authenticator acknowledges the match and allows the user access. If not, the connection is terminated.