Password Authentication Protocol
Password Authentication Protocol (PAP) is a password-based authentication protocol used by Point to Point Protocol (PPP) to validate users.[1] Almost all network operating system remote servers support PAP. PAP is specified in RFC 1334.
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.
- Client sends username and password. This is sent repeatedly until a response is received from the server.
- Server sends authentication-ack (if credentials are OK) or authentication-nak (otherwise)[2]
PAP Packets[]
|
Description |
1 byte | 1 byte | 2 bytes | 1 byte | Variable | 1 byte | Variable |
|---|---|---|---|---|---|---|---|
| Authentication-request | Code = 1 | ID | Length | Username length | Username | Password length | Password |
| Authentication-ack | Code = 2 | ID | Length | Message length | Message | ||
| Authentication-nak | Code = 3 | ID | Length | Message length | Message |
PAP packet embedded in a PPP frame. The protocol field has a value of C023 (hex).
| Flag | Address | Control | Protocol (C023 (hex)) | Payload (table above) | FCS | Flag |
|---|
See also[]
- SAP - Service Access Point
Notes[]
- ^ "Password Authentication Protocol (PAP)". GeeksforGeeks. 2018-07-17. Retrieved 2020-11-08.
- ^ Forouzan (2007). Data Commn & Networking 4E Sie. McGraw-Hill Education (India) Pvt Limited. pp. 352–. ISBN 978-0-07-063414-5. Retrieved 24 November 2012.
References[]
- Lloyd, Brian; Simpson, William Allen (1992). "Password Authentication Protocol". PPP Authentication Protocols. IETF. p. 2. doi:10.17487/RFC1334. RFC 1334. Retrieved 16 July 2015.
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