Configure MIFARE DESFire EV1 as NFC Forum Type 4 Tag for NDEF

Question

I started my studies using NFC in Android. I can easily read and write in NDEF format.

My problem is with MIFARE DESFire EV1 , I have some factory cards and I understand that they do not conform to the NFC Forum type 4 Tag specification and, consequently, do not accept to be read or written in NDEF format (when in their factory configuration).

I can get access to the tag through android.nfc.tech.NfcA or android.nfc.tech.IsoDep .

So far I understand that I need to use IsoDep.transceive() method to pass commands that enable me to build an NFC Forum Type 4 compliant tag.

But I'm having a lot of trouble. I'm using TagWriter and it does the service perfectly. Every time I use the NDEF dataset it automatically performs a routine that makes the card an NFC Forum Type 4 Tag and, consequently, an NDEF tag.

However, I could not find any simple example to do this procedure myself. Even after reading the specification document NFCForum-TS-Type-4-Tag_2.0, I'm still very lost.

Is there any practical example to do the process that the TagWriter application does?

• Recognize NfcA / IsoDep (ok here)
• Make the card conform to the NFC Forum Type 4 Tag specification
• Start recognizing the tag as android.nfc.tech.Ndef
• Enable read and write of NDEF

Answer 1

The procedure to prepare MIFARE DESFire EV1 as an NFC Forum Type 4 Tag (V2.0) is not part of the platform independend NFC Forum specifications. Instead, this procedure is defined by the chip manufacturer (NXP) in their application note AN11004: MIFARE DESFire as Type 4 Tag . The procedure is about the following:

1. If Android already detects the Ndef tag technology, you are done. Since Android tries to detect the NDEF tag application and an NDEF message contained in the NDEF data file, finding the Ndef tag technology means that the tag is already prepared for NDEF (ie it already is configured as NFC Forum Type 4 Tag).

2. Else, you would check if the tag really is a DESFire EV1 tag. You can do this based on the type identification procedure described in AN10833: MIFARE Type Identification Procedure and based on the version information obtained from the DESFire tag.

3. Once you know that the tag is a DESFire EV1 tag (and that you have sufficient access to the master application in order to apply the necessary modifications to the tag, which may require and authentication step), you would first create the NDEF Tag Application. This is a DESFire application that has its ISO 7816-4 DF name (= AID) set to D2760000850101 during creation. The values that you chose for the DESFire AID, the ISO file ID are not important for proper T4T operation (note that this is different for the pre-EV1 generation of DESFire). The key settings depend on your usage scenario. The only other important parameter that you need to set during application creation is to allow ISO 7816-4 file identifiers for files within the application (bit 5 in the Key Settings 2 byte set to '1').

4. Select the newly created application.

5. Create a new standard data file, the capability container file, with a size of 15 bytes. You need to set the ISO 7816-4 file ID to E103 . Make sure to allow plain communication by setting the Com.Set. byte to 0x00. Set the Access Rights field so that you can later modify the file contents during the initialization.

6. Create another new standard data file, the NDEF data file. If you only use the tag as NDEF tag, you would typically use all the remaining available space. Set the ISO 7816-4 file ID to E104 . Make sure to allow plain communication by setting the Com.Set. byte to 0x00. Set the Access Rights field to 0xE000 for a read-only tag or 0xEEE0 for a tag that should allow read and write access through the Ndef tag technology.

7. Select the capability container file and write the capability container data to it:

   \n000F 20 003A 0034 04 06 E104 xxxx 00 yy \n

   where xxxx is the size of the NDEF data file and yy is 0x00 if the file is freely writable or 0xFF if the file is read-only.

8. Select the NDEF message file and write the first 2 bytes as 0x0000 (in order to indicate that the file is empty).

Note that creating the NDEF Tag Application structures on a DESFire (EV1) card requires you to use either the native or the wrapped native command set of MIFARE DESFire. Since some versions of Android cause known problems with the native commands, you are better off using wrapped native commands. You can find details on the DESFire command set in the DESFire product datasheets (available only under NDA from NXP).