Proxmark3 community

blark

Contributor

Registered: 2014-06-16

Posts: 7

Converting from binary to hex for the Proxmark3

Hi all,

I have a few HID readers that I'm reading Wiegand output from, and I want to know if there is a rule for converting from the reader output to a 40-bit hex value to create a card clone on the Proxmark.

For example, when I have a 26-bit card this is the output from the reader:

00001010101110011110011001

I am missing 18 bits of the card: the 7-bit customer code, "ten zeros" and the sentinel bit. I'm having trouble figuring out how to properly calculate the hex without this information.

I am further confused by the fact that I have some 34, and 36 bit cards that obviously do not follow the same format -- so is there some different data that I need to be calculating the hex value?

Thanks for your help!

blark

Contributor

Registered: 2014-06-16

Posts: 7

Re: Converting from binary to hex for the Proxmark3

Just a quick follow up to add a bit more information. I've been researching and on page 12 of the PDF at www.defcon.org/images/defcon-21/dc-21-presentations/Brown/DEFCON-21-Brown-RFID-Hacking-Updated.pdf it says that the first 19 bits of the 26 bit cards are: 7-bit customer code, "ten zeros" and the sentinel bit.

In that case they are:

000000100000000001

and the whole sequence should be...
00000010000000000100001010101110011110011001

Now I can convert to hex: 0x20042AE799

But I'm not sure if that beginning value is what I should be adding, and I'm also pretty sure that won't work with other cards.

carl55

Contributor

From: Arizona USA

Registered: 2010-07-04

Posts: 175

Re: Converting from binary to hex for the Proxmark3

You might want to try reading this older post. Hopefully it will shed some light on your question.
http://www.proxmark.org/forum/viewtopic … 5415#p5415

blark

Contributor

Registered: 2014-06-16

Posts: 7

Re: Converting from binary to hex for the Proxmark3

Thanks, that was very helpful.