This challenge was based off a novel concept for steganography using a rubiks cube. You can read the full paper here: http://docplayer.net/99336533-Rubikstega-a-novel-noiseless-steganography-method-in-rubik-s-cube.html.

Original writeup (https://gist.github.com/nbulischeck/0906e7c75459ffad3141e5c224e383bc).