Tell them to buy a factory that makes computers. That's really the best way to do it; you have to own (or control) as much of the supply chain as you can. Not

Tell them to buy a factory that makes computers. That's really the best way to do it; you have to own (or control) as much of the supply chain as you can. Not really practical if you're a private company who has to compete on thin margins, but not really that hard to imagine for a government. As far as impracticality arguments: keep in mind that each government that maintains a nuclear arsenal (rogue/client states excepted) already has a completely captive technological supply chain, generally at least at a 1950s level, in order to manufacture the weapons in the first place. So if you wanted to build secure nuclear C2 systems, it would make sense to basically build them with the same degree of security, and using the same presumptively-secure supply chains, that are used to create the weapons themselves.