NFC Android: Decode an Mifare tag written with NXP NFC Writer

Question

i`m messing around with some nfc tags, I have written plain text to them with the application 'TagWriter' made by the company nxp. Is it possible to make an application that can read this plain text? or is this impossible due certain authorizations keys of the nxp app? or has someone done this before?

any suggestion is appreciated

Answer 1

The complete documentation on how NDEF messages are written to and read from MIFARE CLassic tags is publicly available, see http://www.nxp.com/documents/application_note/AN1304.pdf and http://www.nxp.com/documents/application_note/AN1305.pdf. The first document lists the authentication keys that are used on page 11 and 12. For the MAD sectors for key A the value 0xA0A1A2A3A4A5 is used and the NDEF data sectors use for key A the value 0xD3F7D3F7D3F7.

Answer 2

NFC does not by default need any special NXP authentication. See the StickyNotes app at http://nfc.android.com .

Answer 3

Which MIFARE tag you have used? There is more then one type... Not that here is also "NXP TagInfo" application - it gives you detailed information about the tag.

Also there are pretty good desktop softwares for USB readers.

Please note that the Ultralight C provides authentication based on 3DES, which might be required for specified memory blocks. I have doubts the NFC Writer supports that - this is probably disabled, so the saved text is plain Text RTD NDEF message in TLV.

BR STeN