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I have the following 3 cards that are identified as an EM41xx format by the proxmark. it appears the printed values are encrypted so as to be difficult to guess the next number.
Printed # - Chip ID - Printed to Hex:
25919337 - 010D774169 - 018B7F69It appears the beginning "01" and ending 2 digits are a direct transfer from the chip ID.
the printed number has a sequence in the first for digits of the decimal number.
My guess is the digits 5&6 of the chip id correspond to digits 3&4 of the Hex of the Printed card number. also digits 7&8 CID = digits 5&6 of the Hex of the printed #
any thoughts?
Last edited by marshmellow (2014-05-02 18:05:37)
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There does not appear to be any encryption being used. It is a standard EM410x format.
Per the EM datasheet, the first 8-bits of the Chip ID is the Vendor Code (0x01 in your examples).
The next 8 digits are the card number (e.g. 0x0D774169 in your first example).
The printed number is normally just a decimal version of the card number (e.g. 0x0D774169 = 225919337).
It appears that your printed card number simply truncated the card number by dropping the first digit resulting in 25919337 which is 0x018b7f69 in hex. I suspect that they had a 9-digit limit on the printer field so the first digit was simply not printed.
Last edited by carl55 (2014-05-01 17:09:10)
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wow... I can't believe I missed that. sorry. and Thanks!
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the thing that threw me off is these come with the first 4 digits incrementing and the last 4 appeared random... I'm going to check to see if any number works in the system or just the specific ones.
Thanks again.
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marshmellow, can you send me a private message. I am interested in getting some cards from you. Thanks.
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marshmellow, can you send me a private message. I am interested in getting some cards from you. Thanks.
So far I have been unable to figure out how to private message on this forum. as an option, my ICQ # is: 6six8fourOO77four
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