Password Authentication Protocol
<networking> (PAP) An
authentication scheme used by
PPP servers to validate the identity of the originator of the connection.
PAP applies a two-way
handshaking procedure.
After the link is established the originator sends an id-password pair to the server.
If authentication succeeds the server sends back an acknowledgement; otherwise it either terminates the connection or gives the originator another chance.
PAP is not a strong authentication method.
Passwords are sent over the circuit "in the clear" and there is no protection against playback or repeated "trial and error" attacks.
The originator is in total control of the frequency and timing of the attempts.
Therefore, any server that can use a stronger authentication method, such as
CHAP, will offer to negotiate that method prior to PAP.
The use of PAP is appropriate, however, if a
plaintext password must be available to simulate a login at a remote host.
PAP is defined in
RFC 1334.