Ntag 424DNA – authentication not possible

[Stephan Zacharias]

Hi community,

since several days I try to authenticate with a NTag 424 DNA Tag without success. The tag is a new tag that has not been specifically configured.
The reader that I am using is: ACR122U-A9

The code I am using to authenticate is:

`
INTAG424DNA ntag424DNA = DESFireFactory.getInstance().getNTAG424DNA(libraryManager.getSupportModules());
KeyData keyData = new KeyData();
byte[] defaultAESKey = new byte[16];
Key keyDefault = new SecretKeySpec(defaultAESKey, "AES");
keyData.setKey(keyDefault);
ntag424DNA.authenticateEV2First(1, keyData, null);
`

When trying with key number "0", then I get a response 9140h (Targeted key does not exist). When I try to do it with "1" I get a 919Dh.

What am I missing? From the documentation it seems to be very easy. Select a key number (0 = master key?), enter the default AES-128 Key and the authentication shall work.

I hope that someone can give me a hint how to use it correctly.

Kind regards,
Stephan

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[TapLinx Support]

Dear Stephan,

These are application keys, which means they work on NDEF Application only and not on PICC level. This means that you need to select NDEF application before trying to Authenticate.

Try something like this:

`byte[] NTAG424DNA_NDEF_APP_NAME =
{(byte) 0xD2, (byte) 0x76, 0x00, 0x00, (byte) 0x85, 0x01, 0x01};

keyData.setKey(keyDefault);

/* this is a MUST */
ntag424DNA.isoSelectApplicationByDFName(NTAG424DNA_NDEF_APP_NAME);

ntag424DNA.authenticateEV2First(1, keyData, null);`

Best regards,
TapLinx team

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