The norwegian Computerworld published an article about a project in which I am involved. The project is part of the current research of Mohammad Derawi, a PhD student from Gjøvik/Norway. The goal of the project is to combine biometric (gait) authentication and token based authentication via NFC.

I have been working on the NFC part in my spare time. We had access to a Google Nexus S smartphone (which is the first android phone with NFC technology) and an ACR122 NFC Reader from Advanced Card Systems Ltd. We used the latest android version (2.3.4) and SDK. On the desktop side we used libnfc and libnfc-llcp (which is a work in progress). The following section provides a short description of how to set up a one-way communication from the phone to the reader.

Google uses the NDEF Push Protocol (NPP) for communication between NFC devices. ANPP packet is wrapped as a NDEF Record in a NDEF packet, which itself is transmitted in a LLCP packet as the payload of the Information PDU (the LLCP and NDEF specifications are freely available on the specs pages of the NFCForum).

The android SDK provides a straight-forward way to create NDEF messages. First you need to add a “Use Permission” item to your manifest and if you want to publish your application on the android market a “Uses Feature” item:

<uses-feature android:name="android.hardware.nfc" android:required="true"/>
<uses-permission android:name="android.permission.NFC"/>

All you have to do now is to create a new NdefRecord and use it to initialize a NdefMessage. Google provides example code on how to create a standard text record (Type Name Format or TNF is well_known, the Record Type Definition or RTD is RTD_TEXT). The following example creates such a NdefMessage and initializes the foreground push feature with it:

NfcManager nfcm = (NfcManager) getSystemService(NFC_SERVICE);
mAdapter = nfcm.getDefaultAdapter();
myNdefMessage = new NdefMessage(new NdefRecord[] { newTextRecord("mymsg", Locale.ENGLISH, true) });
mAdapter.enableForegroundNdefPush(this, myNdefMessage);

The newTextRecord method converts the message to an appropriate encoding. The phone now automatically sends the NdefMessage as soon as a LLCP link is established. The activity which enabled the NdefPush feature has to be active in the foreground though. This restriction also applies to the reading of NFC tags.

On the desktop side we had to build and install libnfc, libnfc-llcp, the acsccid driver from ACS and the following dependencies/required packages (using apt-get and standard ubuntu repositories):

• autotools (packages: autoconf, automake, libtool)
• libusb-dev
• libpcsclite-dev
• opensc

for(int i=19; i < pdu->information_size; i++)
{
	printf("%c",((char)pdu->information[i]));
}

struct llc_service *co_echo_service = llc_service_new_with_uri (connected_echo_server_accept, connected_echo_server_thread, "com.android.npp ");

./llcp-test-server --mode=target