OT: secure http access using PuTTY key files

[Eric]

Good morning...

I have a secure Linux host on which all access is restricted to SSH for 
those with valid PuTTY key files protected with passphrase... no login allowed.

I would like to put up a secure website on that machine that is accessed 
the same way... only those with valid PuTTY key files AND who know the 
passphrase can access.

Where can I go (newsgroups, mailing lists, websites) to learn how to do that?

I know that https uses SSL (secure socket layer) for secure website access 
but I'm pretty sure that doesn't work with PuTTY key files (right?).

Anyway, right now SSH is the ONLY protocol available for external access on 
that machine (everything else tunnels in ssh, e.g. Subversion svn+ssh and 
Filezilla sftp+ssh2) and I'd like to keep it that way if I can.

Is there such a thing as an "http+ssh" protocol?

Also, almost all of the clients that will be accessing this thing are on 
Windows boxen (yeah, I know... nothing I can do about that) using MSIE or 
Firefox.  The web browser would have to be able to access key files 
administered by Pageant (the background-resident PuTTY Authentication Agent).