So my cube-key will look to anybody else as a regular scrambled cube. If my kid finds it and solves it, I'm kind of doomed, right? So what's the plan, I'm supposed to remember the state of the cube?
A admit I'm dumb and lazy - I didn't read the paper, maybe it's covered there - but this sounds quite vulnerable to dictionary attacks, like those phone unlock paass where everybody puts a Z, the cube-keys will mostly be "Solved with red/yellow middles swapped"
It would be interesting if I could take your scrambled cube add my message, scramble it, and then tell you a way to descramble it only on the original unscrambled cube.
It's a novelty. Something more tuned for a scene in a movie than providing security for an individual.
But, the way I see it, you have the traditionally "solved" state cube on your desk(all faces complete), and when you want to use it as a key you "solve" the cube to the state that represents your key.
With a rubiks cube this means you only need to remember the steps of the algorithm that leads you to your key state.