MIFARE card for payment with EMVco compliance

Question

I am working on an NFC-based payment device. I am using MIFARE DESFire EV1 chip.

My question is: How to enable a full EMV compliant payment transaction with this chip hardware?

I found this Visa Ring which does payment transactions. It uses NFC Ring® design of McLear & Co with NTAG IC.

Answer 1

How to enable a EMV payment transaction with MIFARE DESFire EV1?

Simple answer: You can't.

MIFARE DESFire is a proprieatry contactless smartcard system that implements a filesystem for data storage and an access control mechanism (including authentication and symmetric channel encryption). Neither the ISO compliant file IO operations nor the authentication mechanisms implemented in MIFARE DESFire are sufficient to implement any of the EMV specifications for contactless payment systems on top of MIFARE DESFire.

How can there be a Visa payment ring based on NFC Ring (since NFC Ring contains an NTAG NFC tag)?

The Visa payment ring is a special version of the NFC Ring. Instead of one of the two NTAG NFC tags (or instead of both?) it contains a secure contactless smartcard chip (manufactured by Gemalto) that implements the Visa (EMV) payment card application. Hence, the ring contains a dedicated chip for EMV payment.