Any watch can be breached by water, given enough time and pressure. Most watches would not survive very long at the bottom of the Marianas Trench. Similarly, most watches would not survive a few centuries in a shallow pool, even if rated for much deeper immersion.<p>Although no watch can be absolutely waterproof, not even at a given depth, there are levels of risk one can accept. A watch you can use at 100m for several hours a day is effectively waterproof if that&#x27;s the harshest treatment the watch will receive.<p>Similarly, although no cryptographic system is absolutely unbreakable^, there are levels of risk one can accept. And, unlike with watches, we can design cryptographic systems which, except in the face of unforeseen mathematical breakthroughs, or bugs (or backdoors) in their implementation, cannot be broken in the next few hundred years even by a nation state-level attacker.<p>I think is it reasonable to describe a cryptographic system that can&#x27;t be broken within the lifetime of anyone alive today as &quot;unbreakable&quot;.<p>^ Except maybe one-time-pads, depending upon how &quot;unbreakable&quot; is defined.