The trick is to then store it somewhere that anybody who came into posession of it would be unable to figure out -what- master key it was for. If a friend of m

The trick is to then store it somewhere that anybody who came into posession of it would be unable to figure out -what- master key it was for. If a friend of mine has an arbitrary chunk of ASCII stored under their google contacts under a name only they and I recognise, absent rubber hose cryptoanalysis of them it's not going to be an issue, and frankly I don't consider that relevant to my threat model - if somebody's -that- excited about my accounts they'll start with the rubber hose on me at which point all bets are already off.