Just because you can never get full coverage doesn&#x27;t mean it has to be easy. For example, here are some things that could be imlpemented to make firmware backdooring harder:<p>* Certificate Transparency-style public ledger for all firmwares that Apple has signed. Refuse an update if the firmware version has not been published to the ledger. This would make these backdooring attempts public, since we can assume people would watch the ledger and ask questions in case of an unknown version being published.<p>* For open source firmwares, reproducible builds are a great tool to make sure the distributed binaries actually match the publicly reviewable source code. Third parties could recompile the firmware and attest (through signing) that they get the same result.<p>I don&#x27;t know any implementation of either of these two systems, at least publicly available (hint: Bazel does reproducible builds, and you can guess what is driving this requierment). Debian and Mozilla are experimenting with reproducible builds but I don&#x27;t know that it ever reached any useful conclusion.