There is no layered security approach that can fully mitigate malicious hardware. Even if you have a perfect cryptosystem where everything is running fully homo

There is no layered security approach that can fully mitigate malicious hardware. Even if you have a perfect cryptosystem where everything is running fully homomorphic encryption so that plaintext literally doesn't exist, you're still susceptible at the boundaries and to metadata leakages. On real computers you're also susceptible to the hardware simply not executing your code properly and a hundred other things. Since you can't fully mitigate malicious hardware, you have to state a more limited threat model for there to be any useful discussion.