Here is a copy of the internet draft for this protocol.
Here are the source files of a Digest prototype for the WN server. The files wndigest.c and wndigest.h are in the public domain.
This is a link to a document protected by Digest authentication. It can be accessed if you have a client supporting Digest authentication by using username: "Mufasa" and password: "CircleOfLife". No versions of Netscape will work because Digest Authentication is not (yet?) supported by Netscape.
John Franks