The design of the "Devious Digital Device" for Midnight Sun CTF 2019

After last year’s success, Calle asked me to again make a low-level logic circuit challenge for this year’s Midnight Sun CTF, and so this post will cover the “Devious Digital Device” challenge featured in Midnight Sun CTF 2019. I’ll start with a description of the board and how to solve the challenge, and then step back and walk through the design and development process.

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PicoCTF 2018 writeup: A Simple Question

Here’s a walkthrough of my approximate solution path for the problem “A Simple Question” in PicoCTF 2018. This was a fun problem about nontrivial but not particularly advanced SQL injection. There are probably many other good resources on better techniques than those presented here - I am not an avid CTF player, only dabbling in it a little from time to time - but I hope this can serve as a guide for taking the first steps beyond the bare basics of SQL injection.

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Build log: The "Crazy Circuit Conundrum" for Midnight Sun CTF

My friend Calle Svensson (@ZetaTwo) recently arranged the Midnight Sun CTF, and wanted to include a challenge about reverse-engineering a custom low-level logic circuit. He asked me to help, since I have tinkered with just that a bunch lately, and I was very happy to. The result of this became the “Crazy Circuit Conundrum” challenge, and in this post I’ll tell the story of this challenge came to be. This obviously included a bunch of soldering and PCB design, but also some brief Boolean logic reasoning and algorithm design, and of course some mistakes.

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