[mzltest]

*As for the app I'd provide open registration and invited registration. 
Yes, the admin can choose to make registration open or close. There is really a lot of flexibility.

*And by the way,if a student lost connection while on the exam with a time limit, how will you handle it?

This is the only MVP version. People can log in and give exams for the duration of the exam. 

There is not counter cheating mechanism is in place.

This is a bare minimum working Exam application.

Thanks for the reply.
For the continued discussion:
I would store the temporary results in cookie or local storage as in many cases sessions are consuming server resources,which are also more temporarily and as students will want to change their answers often,storing the answers in cookies/localStorage may give the ability for offline-answering in extreme bad connection (if you have prefetched some questions as cache).
I may not encrypt the cookie as if you are not storing these consts you may need to change if often,then it need to be a two-way encryption,thus some additional scripts are needed.Anyway these students can temper with the cookies as long as they don't know the answer.
Or you may try websocket that when their is a property change you send the change to server if you do not like the use of cookies.

For user identity during a exam I prefer sessions,basic user auth might be a strongly-encrypted cookie(or session,I don't think they will stay in the page for days),and for changing the answer or so maybe websocket that sync the changes might be better(authentication first,as always)?