I mean we already have this with AMD PSB. Basically a vendor key is physically burned into the CPU that validates the vendor firmware (BIOS/UEFI) and if the sig

I mean we already have this with AMD PSB. Basically a vendor key is physically burned into the CPU that validates the vendor firmware (BIOS/UEFI) and if the signature doesn't check out, the CPU just refuses to run. I think physical access overriding digital security should largely be fine though, because we have a lot of tamper-evident devices for identifying physical access but you largely can't do that for digital. Like, I can imagine a more consumer friendly PSB using a physical "key" plugged into the motherboard that's essentially a ROM board but using human visible solder pads for the bits of the key. And you could order your own key pair that comes with signing keys from the CPU vendor if you want to sign your own authenticated firmware.