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I created something very similar. It is a PNG and bootable x86 MBR polyglot. When executed, it rewrites the PNG's image data, to convey the program's output. h

I created something very similar. It is a PNG and bootable x86 MBR polyglot. When executed, it rewrites the PNG's image data, to convey the program's output. https://twitter.com/OverTheWireCTF/status/1465742422751821829 https://twitter.com/OverTheWireCTF/status/146574242275182182... Someone who solved the challenge did a writeup: https://joe.lothan.net/ctfs/2021-advent-otw/00-warmup/ https://joe.lothan.net/ctfs/2021-advent-otw/00-warmup/

bowmessage 5y ago
Wow, such an impressive CTF! Did the author solve it in the exact way you intended? I'm curious what the real answer to problem 8 was, now!
- Retr0id 5y ago
  To be honest there is no singular intended solution, I deliberately designed it so that there were multiple approaches that could make sense (especially in combination). Intended solutions include but are not limited to: - Guessing by hand. - Bruteforce by programatically feeding input into QEMU (as in that writeup). - Bruteforce by only emulating the "important" code, via something like Unicorn. - Bruteforce by reimplementing the algorithm in another language (There are some tricks you can use to make it go fast - maybe I should write those up...) - Reducing the search space by grepping for likely keywords. - Bruteforce of remaining bytes of the RC4 key (also as in that writeup).