Coat it in lacquer, then in JB weld metal epoxy, It is possible to break into by soaking in mentholated spirits for an hour, scape off a few softened microns, then repeat, but if you make it thick and they still go to the effort of cloning it, you could encase it in anything and they would still get it eventually, JB weld is just one of the best deterrents i know, seeing as i had to reverse engineer something encased in a thin layer of it, if it was more than 2mm thick i would have given up and rebuilt based on functionality,