HTML - Passowrd For Scavenger Hunt

I want to finish off a virtual "scavenger hunt" with a password which would be given to students after they successfully IM their password request to the on duty librarian. I was thinking I could do some kind of form, but when I looked online for HTML password locked forms, they're all these heavy duty encrypted scripts- and mostly for a fee. What's the easy way to do this?
thanks!
abigail