Blue Gold - DEFCON 33 Gold Bug Writeup

This is the first of several puzzles from the DEFCON 33 Crypto Village GoldBug challenge. I'm writing this for the dual satisfaction of solving the puzzles and getting to show it off. Here I can express and process my experience in solving puzzles. That and so I can have *something* on my website. So we'll start here and expand. I'm working on these puzzles after the challenge period has passed, but I haven't been spoiled on the answers yet.

The above image is the entire puzzle save for the title: "Blue Gold" and a sentence of setting: "Blue Gold beneath Hamunaptra? Or perhaps something else?" A quick search on Wikipedia reveals that Hamunaptra is the famed Egyptian necropolis. With that and the reference to something beneath it, I immediately thought towards steganography. So, being a trigger-happy green-beard, I spent the next half hour messing around with image processing filters and such trying to find a hidden message. This was not the right path.

After exhausting the image processing path, I took a look at the image. Two things jumped out to me. First, the pattern of 3x2 sets of 6 dots is the same layout used in braille. And second, the colors used are similar to the primary colors of light and how they interact. Red, green, and blue being the primary colors, which mix to form cyan, magenta, and yellow. Black is their absence and white is the presence of all three. I was pretty sure this related to how the message was encoded, or at least a hint. However, if braille was correct, that left only four letters to form the secret message, which didn't seem like enough.

Nonetheless, I continued this train of thought. Thinking on the colors of the bugs, I thought about the title of the challege: Blue Gold. "Blue." What if it was braille, and the bugs which had blue light (so blue, cyan, magenta, and white) whould lead to the key? Decoding the puzzle this way, I got the letters "ERBK." I wasn't sure if this was an acronym, so I looked it up, found several unrelated groups and one very strange youtube video by the same name. None were helpful, so I checked if this was the key. It wasn't.

At this point, I wasn't quite sure how to proceed. I managed to get real letters from the braille which felt reassuring, but it also hadn't led me to the key, or a sensible hint. After much more thinking, it finally hit me. There are three primary colors. If one was used to get four letters, the others could probably be used to do the same. Solving for red, I got "PFTA", and for green I got "REOS". The ordering I go lucky on. I figured do the first braille set first for all three colors, then the next and so on. this gives the key: "PREFERTOBASK". 12 letters encoded using fours braille sets and three colors of light. Puzzle Solved.

I was very pleased to have solved this puzzle in only 2.5 hours, and I just love the encoding method. I'll have to play around with similar ideas in the future. Admittedly, I was thrown off by the flavoring of scarabs and Hamunaptra, but overall this was a blast to solve.