The signing key for Firefox stored on a single hardware yubikey available to a single person?
Could be multiple individuals, each with a different key.
https://eprint.iacr.org/2020/540
https://en.wikipedia.org/wiki/Shamir%27s_Secret_Sharing
Multiple hardware devices can have the same key.
alt Hacker News
Could be multiple individuals, each with a different key.
https://eprint.iacr.org/2020/540
https://en.wikipedia.org/wiki/Shamir%27s_Secret_Sharing