Руководство Пользователя для Avaya a500
Cajun A500 ATM Switch Overview
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Cajun A500 ATM Switch User Guide
Password Authentication Protocol (PAP)
The Password Authentication Protocol (PAP) provides a simple method for the peer to
establish its identity using a 2-way handshake. This is done only upon initial link
establishment. After the link establishment phase completes, an ID/Password pair is
repeatedly sent by the peer to the authenticator until authentication is acknowledged or
the connection terminates.
Passwords are sent over the circuit in the clear, and there is no protection from playback
or repeated trial and error attacks. The peer is in control of the frequency and timing of
the attempts. Any implementations which include a stronger authentication method
(such as CHAP) must offer to negotiate that method prior to PAP.
This authentication method is most appropriately used where a plain text password must
be available to simulate a login at a remote host. In such use, this method provides a
similar level of security to the usual user login at the remote host.
Challenge-Handshake Authentication Protocol (CHAP)
The Challenge-Handshake Authentication Protocol (CHAP) is used to verify the identity
of the peer using a 3-way handshake. This is done upon initial link establishment, and
can be repeated anytime after establishing the link. After the link establishment phase
completes, the authenticator sends a challenge message to the peer. The peer responds
with a value calculated using a one-way hash function. The authenticator checks the
response against its own calculation of the expected hash value. If the values match, the
authentication is acknowledged; otherwise the connection terminates.
CHAP provides protection against playback attack through the use of an incrementally
changing identifier and a variable challenge value. The use of repeated challenges is
intended to limit the time of exposure to any single attack. The authenticator is in
control of the frequency and timing of the challenges. This authentication method
depends upon a secret known only to the authenticator and that peer. The secret is not
sent over the link. Use this method when the same secret is easily accessed from both
ends of the link.