Password authentication protocol
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Password Authentication Protocol, sometimes abbreviated PAP, is a simple authentication protocol used to authenticate a user to a network access server used for example by internet service providers. PAP is used by Point to Point Protocol. Authentication is a process of validating a user before accessing the resources. Almost all network operating system remote servers support PAP.
PAP transmits unencrypted ASCII passwords over the network and is therefore considered insecure. It is used as a last resort when the remote server does not support a stronger authentication protocol, like CHAP or EAP (while the last is actually a framework).
[edit] Working cycle
- Client sends username and password
- Server sends authentication-ack (if credentials are OK) or authentication-nak (otherwise)
[edit] 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 | Username | ||
| Authentication-nak | Code = 3 | ID | Length | Message length | Username |
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 |
|---|
[edit] See also
- CHAP - Challenge-handshake authentication protocol
- EAP - Extensible Authentication Protocol
- RFC 1334 – PPP Authentication Protocols
