The ____ authentication type requires encrypted authentication between the server and the client, but uses a generic form of password encryption that enables UNIX computers and other non-Microsoft operating systems to connect to a RAS server.

The authentication type you are referring to is Challenge Handshake Authentication Protocol (CHAP). CHAP is an authentication scheme used by Point to Point Protocol (PPP) servers to validate the identity of remote clients. CHAP periodically verifies the identity of the client by using a three-way handshake. This happens after the initial connection and may be repeated anytime after the connection has been established.

Here is how CHAP works in a step-by-step manner:

1. After the establishment of a PPP link, the server sends a challenge message to the client. 2. The client responds to the challenge with a value obtained by using a one-way hash function (typically MD5). 3. The server checks the response against its own calculation of the expected hash value. If the values match, the authentication is successful. 4. The server may repeat the challenge periodically to ensure that the client's identity is maintained after the initial authentication.

This process prevents the password from being sent over the network in clear text, which would be vulnerable to interception by eavesdroppers.