android - Card emulation via software NFC

Question

After reading a lot of questions, i decided to post this one. I read that stock version of android does not support API's for card emulation. Also, we cannot write custom applications to secure element embedded in nfc controllers due to keys managed by google/samsung.

I need to emulate a card (mifare or desfire etc). The option i can see is doing it via software. I have a ACR122U reader and i've tested that NFC P2P mode works fine with the Nexus-S that i have.

1) I came across a site that said that nexus s's NFC controller (pn532) can emulate a mifare 4k card. If this is true, can i write/read apdu commands to this emulated card? (Probably if i use a modded rom like cyanogenmod)

2) Can i write a android application that reads apdu commands sent from the reader and generate appropriate responses (if not fully, then upto some extent only). To do so, i searched that we need to patch nexus s with cynagenmod. Has someone tried emulating card via this method?

I see that this is possible since we have products from access control companies offering mobile applications via which one can open doors e.g. http://www.assaabloy.com/en/com/Products/seos-mobile-access/

Answer 1

Some facts that may be of help in your quest:

• The NFC controller in the Nexus S (and Galaxy Nexus, Nexus 7 and quite a few other Android devices) is the PN544
• Card emulation can be done either by the secure element connected to the NFC controller or by the host device (=Android device in this case). The Nexus S has a secure element that could be used for that (used in Google Wallet). Card emulation from the host device is not a feature of the PN544 NFC controller, although some claim that they have managed to get it working.
• You can turn on card emulation by the secure element by rooting your device and following the instructions at https://stackoverflow.com/a/10506299/1202968 (haven't tried this with 4.x JB, but I assume that it still works).
• Emulating a MIFARE Classic card can be done by the secure element in the Nexus S, but not by the host device. Emulating a DESFire card is not supported by the secure element in the Nexus S.
• I have investigated a similar doorlock product that used card emulation itself to communicate to an NFC mobile device, while using card reader/writer mode to communicate to access control cards.

IMO, the 2 simplest options are: use P2P communication (Android Beam) or use card emulation in a reader device (if it supports it). All the other options require things like rooted devices and custom ROMs, which are not future-proof and have no possibility to be translated to a real product.