Extremely vulnerable I'm sure. It should be trivial for a hardware backdoor to get the key out of the AES-NI instructions and then have some kind of secret inst

Extremely vulnerable I'm sure. It should be trivial for a hardware backdoor to get the key out of the AES-NI instructions and then have some kind of secret instruction to give the key to the attacker. The attacker would just need to spin up a VM on the same CPU and start extracting keys. But if you already don't trust Intel/AMD you're screwed anyway. Hardware backdoors are really scary and unverifiable.