We’re here! We’re finally here! The gates of Valhalla! What an ancient and robust device! I can’t believe I’ll finally enter Valhalla and join the glorious V8 gang! But how do I open it?

You’ve arrived at the gates of Valhalla. Unfortunately, the gates are closed. There is a control board with a bunch of switches next to the door, and a plaque above saying Only the worthy shall enter the gates of Valhalla. There is a circuit engraved on the plaque. We’ve attached it as a picture to this challenge. Can you open the gates of Valhalla?


We were given the image linked above, and that’s all. But that’s all what I needed. It was pretty clear what we needed, find the input (probably the flag) which gave 1 as the output. I opened the image in Photoshop, zoomed in, put on my favourite megamix from youtube, and started working. It helped me in the beginning to enter the known digits below. (You know the flag is cd21{.*} so the first five letters are cd21{ in binary, and the last is } in binary).

After about an hour of work, I was presented with the flag, almost audible in Pepe’s voice:


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