Can someone tell me how this works?

I'm trying to find a way that allows me to create a separate drupal user id for logging in with from an alias that's posted on all posts and made public in either contact or private messaging forms or anywhere else a user id might normally be presented to anyone else but the user themselves on the site.

From a security standpoint this seems to make pretty good sense. I'm wondering if it's been considered for drupal core and if not, why not.

As it stands right now, my contact and private messaging forms give logged in users access to all user ids, in my drupal 5.2 installation. I've created an alias field for the user id using profiles and have searched to find that there might be ways to change the theming to make userid "invisible" by replacing it with the user alias. But it looks like that user id isn't completely invisible in all places and i'm not sure i want to invest a lot of time implementing a solution that's only going to work 75%.

Also, wondering if it's possible to set up ssl (basic apache certificate) and redirect all user login attempts to https on a drupal 5.2 site. It just occurred to me that all logins are in clear text. So if a site member knows the id of a fellow member, in theory it's that much easier to try a brute force attempt. and snooping doesn't help make that any safer.

thanks much