If I could pay for something completely with something I know and not what I have. I would feel I could leave my house without keys and without a phone or bank card.
So need some form of secure identity that can scale and be secure even on insecure terminals.
Perhaps a combination of password, mobile phone number, PIN and email. Then you could verify the transaction with the email or phone. But you could also opt to not use phone and email for a less attestation that you transacted.
You can often pay with something you wear (with Apple Pay). But I would never depend on it so I do carry a small wallet. And I need keys for my car (which is probably just as well).
So need some form of secure identity that can scale and be secure even on insecure terminals.
Perhaps a combination of password, mobile phone number, PIN and email. Then you could verify the transaction with the email or phone. But you could also opt to not use phone and email for a less attestation that you transacted.