You only need to keep the master password at bank; you can freely update/distribute the encrypted file. Some sort of secret sharing scheme [1] seems like it wo

You only need to keep the master password at bank; you can freely update/distribute the encrypted file. Some sort of secret sharing scheme [1] seems like it would work well here. You can distribute parts of a key so that any 3 of 5 people (or whatever) can work together to recover the key. Unfortunately I don't know of any practical way to do this without kludging together your own system. 1: https://en.wikipedia.org/wiki/Secret_sharing https://en.wikipedia.org/wiki/Secret_sharing