I don't see how this kind of argument generalizes. Short of armored truck deliveries, cryptographically signed digital transmissions are about the only form of

I don't see how this kind of argument generalizes. Short of armored truck deliveries, cryptographically signed digital transmissions are about the only form of information delivery where it's even possible to get this kind of assurance. Yet civilizations have operated for centuries if not millennia on the premise that we deliver things nonetheless. There is no guarantee at all that the government isn't rewriting the New York Times before it hits newsstands, intercepting and changing television signals, swapping out or reading your mail, injecting mind control serum into foods before they reach the grocery store, or that fluoride isn't used to subdue the population (other than science, but you don't know the government isn't intercepting and rewriting published research). The only assurance you get is all these things are illegal. Governments definitely don't universally follow their own laws, but at some point, the existence of some system of laws is either enough for you, or you go live in the woods with a bunker full of seeds and ammo, or start a revolution to replace the government with a new one.