We've been using iPrint internally for a few years now. All of the
printers are unsecure talking down port 631. The user simply clicks to
install and they're off. Now the need has arised to allow the users to
print from the internet. I have this setup and working... almost the way
I want it. Here's what I want to do:

Right now the user can access the iPrint page securely with
https://SERVER/ipps from the internet thru my firewall. The site prompts
them to authenticate and the list of printers appears. They're prompted
to install the client, and then click a printer to install. Because the
printers are not secure, communication, by design I realize, is switched
to port 631 unsecure.
If I don't have this port open a the firewall, it times out. Now I know
the fix would be to go back and make all the printers secure but I'm
trying to keep from doing that. I just need iPrint to prompt for the
login, as it does, and continue to talk securely, but only on the
internet. As it stands now, I have to open port 631 which means if
anyone found out that they could enter http://SERVER:631/ipp on the net,
they could install and print without authenticating.

So in a nutshell, I need an iPrint printer to talk SSL without requiring
authentication. Possible?