Is there a way to force users to change their passwords on next visit?

Let me explain what I am doing...

I had one website that was on Nuke-PHP and I was force to change it over to XOOPS a bit faster then expected. Due to being defaced over and over due to weak azz programming I have no choice.

I am slowly importing users but I have no idea what thier passwords were under Nuke-PHP.

So can I force a change password based on anything OR does anyone know if XOOPS uses the same encryption as Nuke-PHP for the password?

Does anyone have a script to import the users?

Thanks