You're right, storing keys would completely defeat the purpose. We don't do it. Master keys are generated from a user's login information, which we have no know

You're right, storing keys would completely defeat the purpose. We don't do it. Master keys are generated from a user's login information, which we have no knowledge of. Right now if you forget your login/password your account is lost unrecoverably. We have a feature slated that would let you download a file version of your account key, meaning if you lost your username or password, you could log in with the special key file and reset your info. Obviously, you'd have to keep the file encrypted/safe, but that's the user's responsibility ultimately.