I run 10 camera's each year on public land. I use the bear boxes bolted to the tree. For the locks, i picked up the four lock packs so I only carry three keys that will unlock them all.
fact is, if anyone really wants to get a camera they will. I check them about once a week, so that would give someone 7 days to locate one and return with bolt cutters, that is if they didn't have a chain saw with them first.
Locate cameras in out of the way places or above the line of sight. if you find a trail that you think you want to view, then walk up the trail to a more secure location, then walk a little further.