What about when via #2, the government covertly works its way up to obtaining the 3rd party's key? With a 3-party system you now have targets for the biggest pa

What about when via #2, the government covertly works its way up to obtaining the 3rd party's key? With a 3-party system you now have targets for the biggest party to go after. If the US gov gets BigTechSoft's key, then the whole scheme fails. The NSA (gov) has been found doing exactly that already. Back to single point of trust/failure.