在Mifare Desfire中创建标准数据文件

Question

Create File in Mifare Desfire. Return error response like 0x0E DESFire card related exception has occurred. what is the correct command to create files in mifare desfire

CreateStdDataFile(FileNo,Com.Set.,AccessRights,FileSize)
        [8bytes]

public void CreateFile() throws Exception {
    byte[] buffer = new byte[7];
    buffer[0] = (byte) ((0x00)); //file Number
    buffer[1] = (byte) ((0xFF)); //Comm. Sett.
    buffer[2] = (byte) (0x00); // 2 & 3 Access Rights
    buffer[3] = (byte) (0x04);
    buffer[4] = (byte) (0x00);  // 4 & 5 & 6 File Size
    buffer[5] = (byte) (0x00);
    buffer[6] = (byte) (0x0F);

    sendRequest(CREATE_FILE,buffer);
}

try
{
    reader.CreateFile();
}
catch (Exception e) {
    Log.d(TAG, "Problem accessing Desfire tag", e);
} finally {
    try {
        isoDep.close();
    } catch (IOException e) {
        // ignore
    }
}

Answer 1

The problem you are experiencing is endianness . (See in particular the Illustration section.)

The DESFire instruction requires you to pass the file size in the least significant byte order (little-endian), but your code uses the most significant byte order (big-endian).

The way you currently have it in your code ( 0x00, 0x00, 0x0F ) you are not asking for a file of size 0x00000F (15) bytes, but 0x0F0000 (983 040) bytes.

To request a file of size 15 bytes, your code should be:

// ...
buffer[4] = (byte)0x0F;
buffer[5] = (byte)0x00;
buffer[6] = (byte)0x00;
// ...