I'd like to use key based auth so I can SSH to linux systems without needing to specify a password and just worry about keeping the key file safe, but there's a chance that someone else (who that someone is won't necessarily be known in advance) would need to get into those systems in my absence (i.e. if I'm on vacation and unreachable). I'd like to use the same key file for all systems (unless that's a really horrible idea for some reason, I don't know), so I don't want to have to provide this key to anyone else.
I tried googling for an answer but couldn't find one. Can key based auth be used at the same time as keyboard interactive auth?