I would sign ''candidate'' not ''student'' if you are in Canada. Unless your university works differently.
Where I am, in Ottawa, there is no such thing as a difference between a ''candidate'' and a ''student''. The programs are not split into different parts. You do the classes, the research, the lab, the teaching, the writhing when you can (everyone was a different schedule, you do a lot of things at the same time). You do not call yourself a ''candidate'' only at the end, when you are suppose to defend, but all the time.
Also, if I see ''student'' instead of ''candidate'', I will ask myself the question: ''Is this person doing a masters that is class bases (no research that leads to a thesis), just classes and small projects... or does this person really mean ''research based thesis''...
But both should work if everyone remembers that not all universities work the same way and make a distinction between ''student'' and ''candidate''.