Which of the following are the legacy authentication protocols? Each correct answer represents a complete solution. Choose all that apply.

A.
CHAP

B.
MS-CHAPv2

C.
PAP

D.
MS-CHAP

Explanation:
Following are the legacy authentication protocols:
PAP: A password authentication protocol (PAP) is an authentication protocol that uses a password. PAP is used by Point to Point Protocol to validate users before allowing them access to server 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). CHAP: Challenge Handshake Authentication Protocol (CHAP) is an authentication protocol that uses a secure form of encrypted authentication. Using CHAP, network dial-up connections are able to securely connect to almost all PPP servers. MS-CHAP:
Microsoft Challenge Handshake Authentication Protocol version 2 (MS-CHAP v2) is the new version of MS-CHAP. MS-CHAP v2 provides the highest level of security and encryption for dial-up connection in the environment consisting of both Windows NT and Windows 2000/XP dial-up clients. It provides mutual authentication, stronger initial data encryption keys, and different encryption keys for sending and receiving data. MS-CHAPv2: MS-CHAPv2 provides mutual authentication between peers by piggybacking a peer challenge on the Response packet and an authenticator response on the Success packet. MS-CHAPv2 has various features such as:
It is enabled by negotiating CHAP Algorithm 0x80 (0x81 for MS-CHAPv2) in LCP option 3, Authentication Protocol. It provides an authenticator-controlled password change mechanism. It provides an authenticator-controlled authentication retry mechanism. It defines failure codes returned in the Failure packet message field.