Password Authentication Protocol

Password Authentication Protocol (PAP) is a password-based authentication protocol used by Point to Point Protocol (PPP) to validate users. Almost all network operating system remote servers support PAP. PAP is specified in .
PAP is considered a weak authentication scheme (weak schemes are simple and have lighter computational overhead but are much more vulnerable to attack; while weak schemes may have limited application in some constrained environments, they are avoided in general). Among PAP's deficiencies is the fact that it transmits unencrypted passwords (i.e. in plain-text) over the network. PAP is therefore used only as a last resort when the remote server does not support a stronger scheme such as CHAP or EAP.
Working cycle.
PAP authentication is only done at the time of the initial link establishment, and verifies the identity of the client using a two-way handshake.
PAP Packets.
PAP packet embedded in a PPP frame. The protocol field has a value of
C023 (hex).