&gt;Without going into the question of how many bits of entropy that actually has when used with human beings in real settings, and just assume it&#x27;s a perfect check; my question stands: how many people can you find who use this?<p>Probably not very many, but it&#x27;s really only useful for people that ignore basic security features anyway. (Key auth)<p>&gt;When they do: how many of your hosts do you know the image of?<p>None, I use key auth like any reasonable person would.