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.
Point-to-Point Protocol (PPP) can use either Password Authentication Protocol (PAP) or Challenge Handshake Authentication Protocol (CHAP) for authentication. CHAP is used upon initial link establishment and periodically to make sure that the router is still communicating with the same host. CHAP passwords arc exchanged as message digest algorithm 5 (MD5) hash values.
The three-way handshake steps are as follows: Challenge, Response, Success or Failure.
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.
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Periodic authentication after link establish
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