Reading code from RFID card

Question

I have a problem with reading code from RFID card.

Any conversion algorithm exist?

Examples of codes:
04006d0ba0 -> 00008596950352
0d001c59b3 -> 00047253268956
0d001c5134 -> 00047253268674
0d001c9317 -> 00047253265550
0d001c93ed -> 00047253265531
0d001c1b12 -> 00047253261700
0d001c1b1d -> 00047253261707
e800ef0aac -> 00485339628883

Same RFID card, different outputs from different readers...

I know that topic like that exist yet, but i think that is not same problem...

score 2 · Answer 1 · answered Oct 29 '14 at 00:09

The conversion looks quite simple:

Let's assume that you want to convert "04006d0ba0" to "00008596950352".
Take each nibble from the hexadecimal number "04006d0ba0" (i.e. "0", then "4", then "0", then "0", then "6", ...)
Reverse the bits of each nibble (least significant bit becomes most significant bit, second bit becomes second last bit), e.g. "0" (= 0000) remains "0" (= 0000), "4" (= 0100) becomes "2" (= 0010), "6" (= 0110) remains "6" (= 0110), etc.
Convert into decimal number format.

In Java, this could look something like this:

private static final byte[] REVERSE_NIBBLE = {
        0x00, 0x08, 0x04, 0x0C, 0x02, 0x0A, 0x06, 0x0E,
        0x01, 0x09, 0x05, 0x0D, 0x03, 0x0B, 0x07, 0x0F
};

private long convert(byte[] input) {
    byte[] output = new byte[input.length];

    for (int i = 0; i < input.length; ++i) {
        output[i] = (byte)((REVERSE_NIBBLE[(output[i] >>> 4) & 0x0F] << 4) |
                            REVERSE_NIBBLE[ output[i]        & 0x0F]);
    }

    return new BigInteger(1, output).longValue();
}

Reading code from RFID card

1 Answers1