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A Desfire EV1 card outputs the following data over weigand. 3D803DC0. However when I took a look at the Desfire Card, I can see that the data in the file was 1A3D803DC0. Which is the length byte followed by data. I assumed that it is similar to HID Corp 1000 format but looks like Corp 1000 has only a Facility Code / Company ID with Card Number. The data from the card is of the below format.

Example of the Format in Question:

Facility Code : 123 Card Number : 123

26bit Card Data: Hex (3D803DC0) Binary (0011 1101 1000 0000 0011 1101 11) with trailling 0's removed

Format in Question : 1A3D803DC0 (1A = length of Data which is 26)

I would like to know the name of this format. I have searched numerous places but not able to find anything in this regard.

Charan Chakravarthi
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2 Answers2

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The typical format for smart cards is TLV for tag/length/value. I can't recognize from your question, whether your card number is coded as a single byte. There are different variants simple TLV and BER-TLV, which start to differentiate as soon as the length exceeds 127. The document to consider for further information is ISO 7816-4 for the generics and ISO 7816-6 for predefined tags. There you will find, that there are also tags having mnore than one byte and how to code them.

It is not uncommon to have TLV format without the tags, if these are defined at a different place.

guidot
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Firstly, the question was intended to know what format like the HID 26bit Prox (H10301) for example, has a Length Byte followed by the Data. Upon Research found that this was no specific standard format but the implementer of that particular Desfire EV1, wrote the data in the card as the "Length Byte" followed by the data having that length. I also found that the HID Corporate 1000 format was not anything like having a length byte, but was similar to Proximity Formats by HID but with a weird combination of Parity bits, along with the Facility Code and Card Data. This below link illustrates the HID Corp 1000 format

[http://www.pagemac.com/azure/data_formats.php][1]

Having said that, the Desfire Card data was used with Length Byte followed by data, because the implementer of the Desfire Application in the Physical Access Reader, initially reads the length byte and outputs that size of data from the data part, that follows it.

Charan Chakravarthi
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