Shamir secret sharing is a rigorous way to do it. Maybe for this purpose just spreading catenable chunks and some duplicates would be fine though. (It would 'j

Shamir secret sharing is a rigorous way to do it. Maybe for this purpose just spreading catenable chunks and some duplicates would be fine though. (It would 'just' mean one being discovered weakens the overall password, if the finder knows what it is. With SSS knowing any less than all of the shares doesn't reveal any part of the secret.)