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We are reversing the method of creating a byte array packet.

These values are obtained by serialport monitor from mediatek metamode usb port.The values of both packets are changed by changing the imei.

example imei : 534534324234239

 55 00 38 D0 40 01 34 00 03 00 00 00 00 00 00 00
 C8 00 00 00 01 00 00 00 0E 00 12 00 01 00 0E 00
 22 00 18 00 10 EF 01 00 01 00 0A 00 01 00 00 00
 00 00 35 54 43 23 24 43 32 F9 00 00 72

Packet2 is :

55 00 08 D0 00 FF 04 00 00 00 C2 75 C1

We have trouble making packet2, we know last "C1" hex is XOR and the rest are fixed values and do not change.We just do not know by what calculations the value of "C2" in packet 2 was obtained.

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  • Please provide more details of what you are trying to do?
    – auspicious99
    Commented Jan 15, 2021 at 15:43
  • Please provide a sample of multiple packets, ideally 100. That'll make it easier to infer algorithm
    – pythonpython
    Commented Jan 15, 2021 at 18:13
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    i find solution ,first need to reversed hex imei and need Addition byte by byte and output need to Addition with 31, thanks
    – ILYA20
    Commented Jan 15, 2021 at 20:45

1 Answer 1

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solution ,first need to reverse imei array (without F in packet1) and need Addition byte by byte and output need to Addition with 31, thanks

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  • That is super interesting. I think when looking for checksums I've always looked left to right, not right to left.
    – pythonpython
    Commented Jan 15, 2021 at 23:55

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