I'm about to evaluate the possibilities to authenticate with smartphones (Android and Apple) and NFC on existing hardware (which can be programmed regarding the NFC functionality).
So far I have come to the conclusion that Android is supporting this feature directly over the HCE interface but Apple is not supporting this directly only with their own wallet.
So my plan so far is to use the Google/Apple wallet to create a new custom pass that is emulating a NFC tag when the corresponding entry is selected.
This leads to my question: Is this approach possible or am I missing some important point?
Emulating an NFC tag is not possible in Apple Wallet or Google Wallet. Both extend the ISO 14443 EMV standard through the Apple VAS and Google SmartTap protocols. Both protocols are only available under NDA.
For Apple VAS, the polling loop of the reader needs to be modified in order to have the correct pass automatically display on the lock screen. Both protocols have different dialogues and decryption algorithms.