My manager built a Gameboy emulator last year for a side project, and he was explaining to me the genius authorization mechanism that the Gameboy used: Every ga

My manager built a Gameboy emulator last year for a side project, and he was explaining to me the genius authorization mechanism that the Gameboy used: Every gameboy game starts up by showing the Nintendo® logo. The system checks the displayed value against a known checksum (or hash or something) that has to be perfect or the software won't go to the next instruction. So in order to make an unauthorized game for Gameboy, you have you put Nintendo's Registered Trademark as the very first thing that appears on your game, without permission. So instead of a technical limitation which can be broken with enough effort and engineering, you have to simply violate well-established Trademark law. Pretty smart.