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Password authentication protocol

Password authentication protocol definition

Password authentication protocol (PAP) refers to a simple, two-step authentication process that consists of the user sending their username and password to the server in plain text and the server that sends a response. While the PAP has been largely replaced with more secure alternatives, a few exceptions remain such as internal network communication as it doesn’t require high security standards.

See also: end-to-end encryption, SFTP server, man-in-the-middle attack

Weaknesses of the password authentication protocol:

  • Lack of encryption. PAP uses plain texts, making the data susceptible to eavesdropping and interception.
  • No protection against playback attacks. Without a timestamp or session identifier in the authentication request, the message can be captured and replayed later.
  • Man-in-the-middle attacks. PAP authentication only works one way, making the data susceptible to MITM attacks.

Password authentication protocol alternatives:

  • Challenge Handshake Authentication Protocol (CHAP). CHAP is a secure authentication protocol that uses a three-way handshake process. It sends a random challenge string to the user, which the user encrypts and sends back to the server for verification. Repeating this process several times helps ensure that the authentication process is secure.
  • Extensible Authentication Protocol (EAP). EAP supports multiple authentication methods, including digital certificates, smart cards, and biometric authentication.
  • Lightweight Extensible Authentication Protocol (LEAP). LEAP is a proprietary authentication protocol from Cisco. It uses a two-way handshake process and supports mutual authentication to prevent spoofing attacks.