The idea of the project is that it's supposed to be crack-able. So a OTP is probably out. Otherwise K4 is just random noise and not an obscure puzzle.

Or if he made a mistake (because he has no idea what he is doing), it is uncrackable.

When I was a kid, I had this idea that I was excited about, that I'll write meaningless codes in pieces of paper and strategically place them to drive people who try to figure out crazy. People just didn't care.