Which authentication sends a username and a password that is not encrypted?

Anonymous
Password Authentication Protocol
Digest authentication
Windows authentication

Answer:

Password Authentication Protocol

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When using VPNs, Windows 7 and Windows Server 2008 support the following forms of authentication:

• Password Authentication Protocol (PAP):
  Uses plain text (unencrypted passwords). PAP is the least secure authentication and is not recommended.
• Challenge Handshake Authentication Protocol (CHAP):
  A challenge-response authentication that uses the industry standard md5 hashing scheme to encrypt the response. CHAP was an industry standard for years and is still quite popular.
• Microsoft CHAP version 2 (MS-CHAP v2):
  Provides two-way authentication (mutual authentication). MS-CHAP v2 provides stronger security than CHAP.
• Extensible Authentication Protocol (EAP-MS-CHAPv2):
  A universal authentication framework that allows third-party vendors to develop custom authentication schemes including retinal scans, voice recognition, fingerprint identifications, smart cards, Kerberos, and digital certificates. It also provides a mutual authentication method that supports password-based user or computer authentication.