Микроконтроллеры

google: "The FTDIChip-ID is a unique, 32-bit number that http://www.ftdichip.com/Documents/ProgramGuides/SafeGuard%20IT%20V1.0%2009_08_07.pdf

is burned into the device during manufacture and is readable over USB, thus forming the basis of a security dongle that can be used to protect customer application software from being pirated. Neither product manufacturers nor end users can change the number by any means.