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philheath

Contributor

Registered: 2017-03-22

Posts: 4

[solved] Mifare parity - how to?

Hi!

For authenticate with ke a for block 1 it s known that 60 01 command should be sent to get the card nonce.

CRС for that would be 7C 6A

So the command with crc is 60 01 7c 6a

But now i'd like to manually add parity bits and this is were i'm stuck

I know that the final result is 60 03 F0 51 0B (cmd + crc + parity)

But I'm unable to get the result

60 01 7c 6a is in binary

0110 0000 000 0001 0111 1100 0110 1010

As i understood it should be in lsb, so it is as follows:

0000 0110 1000 0000 0011 1110 0101 0110

adding odd parity:

0000 0110 1 1000 0000 0 0011 1110 0 0101 0110 1

here's where i'm stuck - don't know how to group its to have 5 byte (how and where i should add 4 bits)

I tried as follows:

i grouped these bits by 8 bits and added 4 zeros to the end

00000110 11000000 00001111 10001010 11010000

then i converted back to msb:

01100000 00000011 11110000 01010001 00001011

this makes 60 21 F0 51 0B but not 60 03 F0 51 0B so there is a mistake in the second byte. What's wrong with my logic, any suggestions?

(yeah, i need to handle crc + parity on the software side rather than on proxmark side)

UPDATE: I made a mistake in the second byte - i misspelled 10 rather 01

Now it's ok but maybe it should be sticky on how to calculate parity

Last edited by philheath (2017-03-28 16:39:37)

marshmellow

Contributor

From: US

Registered: 2013-06-10

Posts: 2,302

Re: [solved] Mifare parity - how to?

makes me curious as to what you are doing?