There's a lot of information about reverse engineering some of the older CPUs around e.g. the MOS6502 (NES, Apple II, C64, etc). This is a great presentation s

There's a lot of information about reverse engineering some of the older CPUs around e.g. the MOS6502 (NES, Apple II, C64, etc). This is a great presentation showing how this CPU is reverse engineered: https://www.youtube.com/watch?v=fWqBmmPQP40 https://www.youtube.com/watch?v=fWqBmmPQP40 Basically it comes down to the fact that you can't really hide transistors and ultimately that's something you can reconstruct. It sounds like a lot of work, and it is, but if you do it you can perfectly emulate a chip. If you can dig out non volatile memory then potentially you have the firmware. Once someone has their hands on that it'll be broken, almost guaranteed, as it becomes a software problem. Lots of people are very good at assembly hacking.