"Login" for file retrieval

Say I have 30 graded exams that have been OCR graded and annotated in PDF form.

They are in the format of studentnumber.pdf (e.g. 111101.pdf).

How can I allow the students to retrieve it?

My first idea was to dump all the files into my website /~name/handback/ and then create a java script input box that asks for the student number x and then opens the corresponding x.pdf. How could I do this?

I don't think this is a good method however, since a student who knows another's id can download their entire exam. How could I fix this? If I were to get each student to give me a password at the beginning of the term how could I store and use them?