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I have used two RFID readers (different vendors), which provide two different identifiers for the very same RFID tag:

  • Reader A shows 5BFA0746 (decimal 1543112518)
  • Reader B shows 4607FA5B (decimal 1174927963)

Can you explain why? There are no similarities with the last bytes nor prefixes.

Kristian
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2 Answers2

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I'm not sure that I completely understand your question, but the two values are identical except for their byte-order. Hence, both readers do read the same value (possibly an ISO/IEC 14443-3 UID/anti-collsion identifier?). They just present them in reversed byte order:

          +--------+--------+--------+--------+
Reader A: | Byte 0 | Byte 1 | Byte 2 | Byte 3 |
          |   5B   |   FA   |   07   |   46   |
          +--------+--------+--------+--------+
Reader B: | Byte 3 | Byte 2 | Byte 1 | Byte 0 |
          |   46   |   07   |   FA   |   5B   |
          +--------+--------+--------+--------+
Michael Roland
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  • Thanks! Using the tool [TWNconfig](http://www.papercut.com/kb/Main/ElatecFirmwareForToshibaMFP), I was able to reconfigure one of the RFID readers. – Kristian Oct 13 '15 at 09:51
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I can think of two reasons this may be happening:

1) CRC or checksum calculations at the start vs. end of the tag ID (vendors may implement this differently) but it sounds like you've already investigated that

2) The readers are configured to read different areas of the tag. For example, are you sure you are getting the tag ID in both cases? For passive UHF RFID Tags, you might be configured to read the TID Serial # vs. EPC. For HF MiFare readers, perhaps you are reading a data bank on one reader and the ID in the other. This is a long way of saying, are you sure both of your readers are actually configured the same way?

snoopaloop
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