Wireless Communication Question:

Challenge-Handshake Authentication Protocol authenticates to an authenticating entity of a user or network. The entity can be an Internet access provider. CHAP is used by Point-to-Point Protocol that servers for the validation of identifying of remote clients. The identity of the client is verified by CHAP periodically with the use of a three-way handshake. This situation occurs when an initial link is established and maybe repeated after at any time. The shared secret is the base for verification. CHAP protection to play back attack by the peer. This is done by using an incrementally changing identifier and of a variable challenge-value. Both client and server need to know about the plain text of secret which uses CHAP.