Android NFCAdapter - Issue with AuthenticateSectorWithKeyA & Hex

[BoolTech]

Developing Android App in .net Maui. Having issues with NFCAdapter, specifically passing a specific sector key with AuthenticateSectorWithKeyA.
We print and encode our own Mifare 1K cards. Print software allows us to change the sector key A. I have tried multiple, and all ok, but need a specific key to work which is failing authentication.

No problem passing the following Keys and authenticating the sector with AuthenticateSectorWithKeyA.

byte[] keybytes = new byte[] { (byte)0xff, (byte)0xff, (byte)0xff, (byte)0xff, (byte)0xff, (byte)0xff };
OR
byte[] keybytes = new byte[] { (byte)0xAB, (byte)0xCD, (byte)0xEF, (byte)0x12, (byte)0x34, (byte)0x56 };

var auth = tag.AuthenticateSectorWithKeyA(0, keybytes);

All ok, var auth = true

But when I try the following Key it fails to authenticate. var auth = false.

byte[] keybytes = new byte[] { (byte)0x19, (byte)0x23, (byte)0x86, (byte)0x18, (byte)0x05, (byte)0x00 };

HEXString is 192386180500

Only thing I can see if the last two bytes have a zero prefix

SO
Tried:

byte[] keybytes = new byte[] { (byte)0xAB, (byte)0xCD, (byte)0xEF, (byte)0x12, (byte)0x34, (byte)0x56 };
Result: OK - var auth = True

Tried:

byte[] keybytes = new byte[] { (byte)0x19, (byte)0x23, (byte)0x86, (byte)0x18, (byte)0x05, (byte)0x00 };

Result: Fail - var auth = false

Use this key with non android RFID readers and all is ok. Need to use this key as we have produced thousands of RFID cards with this key A for sector 0.

Bit new to Hex and byte arrays, any help welcome.

 

[Unforgiven]

Development thread moved to the dev area for better exposure.

 

[saramarz]

It's possible that the issue may be related to the way that the key is being converted to a byte array. Make sure that you are using the correct syntax to convert the hexadecimal string to a byte array.

Here is an example of how you can convert the hexadecimal string to a byte array:

string hexString = "192386180500";
byte[] keybytes = new byte[hexString.Length / 2];
for (int i = 0; i < keybytes.Length; i++)
{
  keybytes[i] = Convert.ToByte(hexString.Substring(i * 2, 2), 16);
}

Alternatively, you can use the BitConverter.GetBytes method to convert the hexadecimal string to a byte array:

string hexString = "192386180500";
byte[] keybytes = BitConverter.GetBytes(long.Parse(hexString, System.Globalization.NumberStyles.HexNumber));

Once you have the keybytes array, you can pass it to the AuthenticateSectorWithKeyA method as usual.

It's also a good idea to double-check the value of the key that you are trying to use, as it's possible that there may be an issue with the key itself.

I hope this helps! Let me know if you have any questions.