Calculate Mifare UID BCC

Yuvutuser · 2015-02-12 00:44:54

Hi! so i was trying to use a chinese card with my proxmark, and it won't change the uid, but then i tried with an ACR122U reader using Mifare classic recovery tools beta V0.1 and it worked! but the thing is i tried then to change the uid to a random one, and it won't work. I'm guessing i need to put the right BCC, so here is my question: how do you get it? Sorry if it is already here, i tried to find it but i couldn't. Thanks!

asper · 2015-02-12 01:15:03

Xor of the 4 UID bytes.

Yuvutuser · 2015-02-12 05:08:31

Thanks! That works!

iceman · 2015-02-12 10:02:10

if you are using a magic chinese tag, and the "hf mf csetuid" then it should work with just giving it a UID...

Yuvutuser · 2015-02-25 06:05:43

Hi, iceman i tried with proxmark and it didnt work. I just made an app to calculate it quick. Its for a 4 byte UID. Please let me know what can i do to improve it. Thanks. https://play.google.com/store/apps/details?id=app.bcccalculator

roman921 · 2016-05-13 19:48:54

I get mifare classic card with direct change uid. I write uid with incorrect BCC byte. Now acr122 don't see card. Please, write, how restore this card ?

ikarus · 2016-05-29 16:35:07

Hi there!
So I'm working on a BCC checker and calculator for Mifare Classic Tool right now.
The calculator is pretty much strait forward: Take the 4 byte input and xor them.
However, I have come across difficulties when it comes to the BCC check routine.
This routine should prevent people from writing wrong manufacturer blocks (block 0).
As you can see by roman921's request, those things happen.

For a 4 byte UID this is simple: The 5th byte of block 0 has the be the BCC of the UID.
But what is about 7 or 10 byte UIDs? The document by NXP only describes the
calculation of the BCC during the anti collision phase. Does anyone of you guys
know if the BCC(s) of a 7 or 10 byte UID is also stored in a block 0?

This is a block 0 of a original NXP Mifare Classic 7 bytes UID tag:

04395CF2201D80184200040111001810

Can anyone spot any BCC values in there?

Any help is welcome
Cheers
ikarus

iceman · 2020-08-19 01:44:28

Sniff a anti-collision phase between a genuine reader and genuine tag and compare the data?

Proxmark3 community

Announcement

#1 2015-02-12 00:44:54

Calculate Mifare UID BCC

#2 2015-02-12 01:15:03

Re: Calculate Mifare UID BCC

#3 2015-02-12 05:08:31

Re: Calculate Mifare UID BCC

#4 2015-02-12 10:02:10

Re: Calculate Mifare UID BCC

#5 2015-02-25 06:05:43

Re: Calculate Mifare UID BCC

#6 2016-05-13 19:48:54

Re: Calculate Mifare UID BCC

#7 2016-05-29 16:35:07

Re: Calculate Mifare UID BCC

#8 2020-08-19 01:44:28

Re: Calculate Mifare UID BCC

Board footer