There are multiple NFC cards, I think it's using Shamir secret sharing to reconstruct the secret.
The keynote video is pretty instructive. A lot of marketing (as it should!) but nevertheless explains all the great tech they are using. Super damn impressive.
yeah, this is something that tapsigners do except only with multiple individual keys using protocol musig... musig2 support with schnorr would work too but that's a whole protocol change, shamir's secret shares would be fine for the interface side of it
it's a hard problem, i can see a lot of people falling back to methods that have wide open physical vulnerability, but this is more of an issue for travelers than people working in an office or at their home where there is physical security
You are correct
