What is Password Authentication Protocol?

Password Authentication Protocol (PAP) is a simple, widely used authentication protocol that transmits usernames and passwords in plain text over a network to authenticate users. It is primarily used in Point-to-Point Protocol (PPP) connections and early dial-up networking.

Here’s how PAP works:

The client sends a request containing the username and password to the server.

The server checks the credentials against its database.

The server grants access if the credentials are valid; otherwise, access is denied.

PAP’s major drawback is that it transmits the password in an unencrypted format, making it vulnerable to interception by attackers, especially over insecure connections. Because of its lack of security, PAP is rarely used in modern networks where more secure protocols like CHAP (Challenge-Handshake Authentication Protocol) or EAP (Extensible Authentication Protocol) are preferred. When PAP is used, it should always be paired with secure transmission through a VPN or encrypted connection.