problem with read/write data from mifare4k in 6212

[EOZz]

Hi to all!
I have some trouble with my 6212. On this phone was used next code:

	byte[] KeyA = {(byte)0xa0, (byte)0xa1, (byte)0xa2, (byte)0xa3, (byte)0xa4, (byte)0xa5};
	MFKey.KeyA key = new MFKEY.KeyA(KeyA);

	byte[] arr = new byte[16];
            for(int i = 0; i < arr.length; i++)
                arr[i] = 0;

            for (int i =0; i<256 /*all blocks*/;i++)
            {
                WriteBlock(i,arr,key); /* write arr[] in Block(i) with access by "key" */
            }

so it set all data in mifare4k to zero successfully (main idea was delete all data).
But ofcourse I have got a problem now, I can't read or write something there. I use various keys (standard and zero-keys), use KeyA and KeyB for access.. I read access bits, it show that I can read/write data. But it does not help..
Have you any idea? What should I do for read/write data now? And what I lose sight of?

[mroland]

Hallo EOZz,

with this code you have set all blocks of the MIFARE card to 0x00000000000000000000000000000000. This means that for each sector you also set the sector trailer to zero. Thus you set key A, key B and the access bits to zero as well. For key A and key B this would not be too much of a problem as they would then simply be 0x000000000000. But setting the access bits (i.e. bytes 6 to 8) to zero is a big problem.

The problem is this: Bytes 6 to 9 contain each a non-inverted and an inverted version of each access bit. Thus, if all bits are zero this is certainly an invaild value (as for each access bit that is 0, the inverted version would need to be 1). From the MIFARE documentation:

Remark: With each memory access the internal logic verifies the format of the access conditions. If it detects a format violation the whole sector is irreversible blocked.

Therefore, I would expect that your card is irreversibly damaged.

br,
Michael