Dynamically changing a timestamp - suggestions?

Question

I'm writing up an online examination site for an educational institution. Time limits can be set for each assessment, and once a user begins an exam, a new timestamp is created on the server. The problem is that our school computers often lock up and students are forced to restart, losing exam time.

I figured out I could store the timer as a cookie, but that could easily be compromised. Any suggestions? Thanks.

Answer 1

You could store a timestamp in a database that is linked to their user (I would assume they have a login if they are doing exams) and perform an ajax call every few seconds to check if they are still online.

In this ajax check you can update the database with a new timestamp that indicates when they were last online, so if the computer locks up and they have to restart you can figure out how much time was lost.