Staying a month up in the mountains?

Me and my brother, (both of us are 18) want to go on a month long camping trip type scenario, we want to go into the mountains, in a secluded area, with nothing but clothes, a tent, and flint, we want to learn to appreciate what we have in our homes, and get in shape to a certain extent, were both decently in shape, but over the winter we gained a bit of weight, regardless, what i'm asking is: is anything were wanting to do illegal in any sense, and is there anything else we should bring along as a necessity, thank you in advance :)