> tap a RFID hanko

we call those contactless smart cards

RFID isn't smart; it's just a little chip that harvests energy from being illuminated by a radio wave signal from the terminal, and reflects back a code. (Well, that's a passive tag; there are self-powered ones also.)

Smart cards contain a considerable embedded system for transactional processing; it's quite different from just transmitting an ID.

Correct. These IC cards [1] do some cryptography, right?

[1] https://aruarian.dance/blog/japan-ic-cards/

That's not correct. Smartcards are any cards with chips, RFIDs are any cards/tags with radios. Neither has to do with cryptography.

[deleted]

> RFID isn't smart

Makes it utterly useless as a digital signature then.

Correct; an RFID tag cannot hold a cryptographic secret and perform a calculation with it to prove that it knows the secret, without revealing the secret. It has no compute capability. It's just a kind of reflective beacon.

False: RFID is a communications technology that doesn’t restrict the use of a “smart” processor.

EMV, NFC, and RFID are all related technologies which may underlie “tap to pay / sign” features.

https://en.wikipedia.org/wiki/Contactless_payment

Falsely false.

RFID: Radio Frequency Identification: passive powered by RF, returns data when powered.

NFC: Near Field Communications, is a protocol for communications, built on RFID, includes polling for readers and protocols for defined crypto and data storage/retrieval.

EMV: Eurocard/Mastercard/Visa standard for the data and crypto operations for an EMV chip, extended from physical by the use of NFC for contactless payments, primarily by replicating the data on the magstripe and adding some additional crypto and dynamic elements.

EMV is one standard for how to use an NFC card, there are others, primarily used for transit.