CHAP

networkingsecurity

Stands for: Challenge-Handshake Authentication Protocol

The Challenge-Handshake Authentication Protocol - PPP's secure alternative to sending a password in the clear.

CHAP authenticates by challenge and response: the authenticator sends a random challenge, the peer replies with a hash of the challenge plus a shared secret, and the secret itself never crosses the wire. It can also re-challenge mid-session. Microsoft's MS-CHAP variants extended it. It is the safer of PPP's two authentication options - the other, PAP, sends the password in plaintext - and the pattern recurs throughout network authentication.

Also known as: chap, ms-chap, challenge handshake

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