QR Code reverse engineering

QR Code reverse engineering

Hello everyone! I’m currently looking into producing a generator that can regenerate the following QRs from their raw byte payloads, of which are both:

  • Mask Pattern 3
  • Error Correction Level(ECL): M
  • Version 2 QRs

From what I can derive, the raw byte payloads for each respective QRs are as follows:

  • 41 ac 49 1d 80 d0 e3 9d d8 dc 87 73 ea 6a aa dc 31 b0 10 50 8c 94 42 83 e6 15 ce f0
  • 41 ac 1b d1 a8 93 c2 23 83 6a 01 73 77 cd 18 1dc3 6d ae c2 ea 56 f4 db 3a a6 1e b0

However, from the packages I have used so far, I always end up with a 41 a4 as the header value.

I have tried:

I do understand 41 does determine the version, but I am confused onto how ac is derived. There are also QRs that have ad instead of ac, but the ECL and Mask Pattern are different if I recall.

https://preview.redd.it/4vuw0y7kbqla1.png?width=1000&format=png&auto=webp&s=16a093e614e43942c25853261fe5d25e613d9e70

submitted by /u/SmoothMilkTea
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March 4, 2023
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