There are or shortly will be convincing fake pictures and videos, voice clones, and programs that can imitate someone’s writing. We need to put in place usable authentication among family members.
For example,
“I’m at the gas station without my wallet. I need the credit card number to pay for the gas.”
“I’ll bring it out. Where are you?”
“Pittsburg; just read me the number.”
[This would be ridiculous, except it’s happening over Facetime, or it’s a convincing voice clone.]
“Pittsburg!? Authenticate possum.”
“The code’s in my wallet.”
[That’s not the way we’re supposed to do it…]
Hang up at once.
I don’t know of a bullet proof authentication protocol, and I’m wary of making up stuff. There’s probably something well-researched out there. It seems like it would include an off-line paper list of secret words, used once and then crossed out, and maybe some other stuff not written down. The papers should be distributed in person, and would need to be in pairs – not one for the whole family.
The whole business will be a hassle. This kind of thing can be like having a second job, so it has to be something busy human users can really do. Hopefully it won’t be necessary for day-to-day interactions.