Which two statements about using the CHAP authentication mechanism in a PPP link are true?
(Choose two.)

A.
CHAP uses a two-way handshake.

B.
CHAP uses a three-way handshake.

C.
CHAP authentication periodically occurs after link establishment.

D.
CHAP authentication passwords are sent in plaintext.

E.
CHAP authentication is performed only upon link establishment.

F.
CHAP has no protection from playback attacks.

Explanation:
CHAP is an authentication scheme used by Point to Point Protocol (PPP) servers to validate the
identity of remote clients. CHAP periodically verifies the identity of the client by using a three-way
handshake. This happens at the time of establishing the initial link (LCP), and may happen again
at any time afterwards. The verification is based on a shared secret (such as the client user’s password).