How does HTTP Digest Authentication work?

A.
A wrapping envelope is constructed including the message body, the client’s SSL certificate,
and a master secret value, and sent to the server.

B.
A one-time use token (nonce) is generated by the server and sent to the client, where it is then
returned on each subsequent request.

C.
A digital signature is computed on the entire message body using the client’s private key and
subsequently included along with the request for all future communications.

D.
A one-time use token (nonce) is generated by the server and sent to the client, where it is then
used in a computation of a hash involving the username, password, nonce, and some other
values.

Explanation: