Wow. I was involved in the game genie development and you might like to know the only reason we encrypted the codes was because the we were scared of being sued by Nintento (rightly as it turned out) and we figured naively that it would help if people couldn't make up their own codes. During the court case (nintendo did indeed sue us). Ironically the lawyers told us it was the other way round so we actually published hints on how to experiment making new codes by trial and error.