[lsedgwick]

To add on with another question, are there systems (like password managers, or others) which have "double password" as a first-class feature? For instance, a hacky way could be if personA knows passwordA only, and personB knows passwordB, and the literal password for a system is the concatenation "passwordA + passwordB" - you could get that if both people sat at the same keyboard (or did something else annoying), but a password manager for instance would need first-class support for that feature to be able to have the two individuals launch a shared session to enter both passwords. Or I would even love a system where if at least 2 out of 3 people entered their passwords it launched a shared session: no one single point of failure either for compromising a person or for that person getting hit by a bus.

[sebk]

Have a look at https://mitxela.com/projects/shamirs_password_store for an explanation of a suitable algorithm for this use case.