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RFID algorithm for obtaining a card identifier

I get bytes from the RFID reader when presenting the card, but I cannot figure out how to get the card ID from these bytes.

For example, I have a card on which these numbers are printed: 0007625328 116.23152 . I would expect this to be the identifier of this card, right?

For this card, I receive the following bytes from the reader (in hexadecimal notation): <42 <09 <01> <74 <00> <74 <5A> <. 70>

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The decimal number 0007625328 is converted to 0x00745A70 in hexadecimal notation.

The number 116.23152 is actually another representation of the same value (0007625328):

  • 116 in decimal format 0x74 in hexadecimal format.
  • 23152 in decimal format 0x5A70 in hexadecimal format.
  • Combined, this also gives 0x00745A70 .

So, the value you get ( 42 09 01 74 00 74 5A 70 ) seems to be a concatenation of some form of prefix value ( 0x42090174 ) and the serial number of the printed card ( 0x00745A70 ).

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