Ask YC: What are the best computer science universities in Canada?

I'm considering a move to Canada sometime in the next year or two, but I plan on going to grad school (I'm on track to finish my BS in CS in the next two years). If I do decide to make the move, what are the best computer science schools, preferably with significant research in security? I like the Vancouver area, but I don't think the University of British Columbia would be a good pick for CS. Opinions?

Also, it would be nice, but not necessary, for there to be some amount of startup activity in the area.