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

A.
CHAP users a two-way handshake

B.
CHAP authentication periodically occurs after link establishment.

C.
CHAP uses a three-way handshake

D.
CHAP authentication is performed only upon link establishment.

E.
CHAP authentication passwords are sent in plaintext.

F.
CHAP has no protection from playback attacks.