[hlandau]

The NFC chip I want still doesn't exist: a CPU and flash I can write a program for, directly, no VMs, no Java, without an NDA'd datasheet.

These exist, but they're all behind NDAs and you're not allowed to have them. They're used for e.g. EMV.

[Gibbon1]

I saw an NFC chip that has 512 bytes of eeprom. Talks to a micro via I2C and has an interrupt that can be used to wake it up.

I think it's a M24LR04E.

Costs like $0.50.

I think these could be useful for devices where you have a limited amount of data you want to read or transfer. Like why have bluetooth and all the crap that entails when all you want to do is configure a device once.

Advantage of a separate IC is you can use it with whatever microcontroller development stack you have working.

[crote]

The problem is that it is simply a dual-interface EEPROM. It only holds data, it doesn't process it. Great for something like a device whose configuration you can update via NFC tap (think e-paper display), not so great if you want to do a whole challenge-response dance between microcontroller and NFC smartphone.

[hlandau]

See comment below.

More generally what I'm seeking is something in the card form factor which is suitable to store cryptographic secrets (i.e., a smartcard).

Separate IC is a disadvantage here since it creates a vulnerable security boundary and makes it infeasible to integrate the chip into a thin card.

[userbinator]

How about something like this:

https://hackaday.com/2009/06/27/avr-rfid-tag/

[bsder]

Is there a problem with the TI NFC chips? They all seem to be purchasable and have available datasheets.

[G4E]

You should check out the lpc8N04 from NXP then ;)

[hlandau]

This is interesting but clearly not intended for security/cryptographic applications... no security hardening, no hardware cryptography, and it's also not available in a card form factor according to the datasheet.