Category CTF

This year I was at bruCon in Ghent, BE. I usually either go to interesting talks or spend the conferences in challenges just like I did in Defcon back in 2017.

So during bruCON I stumbled upon this challenge with QR-code that says “first one to scan this gets 100€”; in my head I thought pff this is easy and I will probably not be the first one to scan this. So I popped my phone and scanned. Nothing happened. Then I was like oh wait .. a huge piece of this qr-code is missing.

So the first thing I thought of is to mark the squares randomly because I thought it must be redundant or error correction squars. Remember at this point I know nothing about qr-codes...

If you missed this one; please head to this link, and try it yourself before going to the solution.