Password Authentication Protocol

    (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.

   (1996-03-23)