WordPress MU

Is it possible to get WP MU to authenticate RSS feeds?

I know there is another post in the forums that says most aggregators dont support authentication but this is not an issue for this particular application.

I just need the feed to be secure - encryption would be nice as well but authentication is a good start :)

Many thanks

Andy

Um, I'm a bit lost here. My RSS feeds pass the validators.

or am I missing something here?

Not source validation, user authentication. ;)