[crote]

Don't most (all?) modern CPUs have an embedded TPM? Plug-in TPMs were indeed a thing early on, but I thought that was a thing of the past by now. You can't exactly get in between the CPU and another part of the same CPU.

Also, isn't the EK (and therefore its cert) unique per-device, allowing you to tell it apart? The fact that the manufacturer used the same upstream key to sign both certs doesn't matter, just like a CA can sign multiple TLS certs with one root key.

[whiatp]

Yeah, if the CPU has a an embedded TPM that would be way better than the external ones. I'll admit that my experience comes from somewhat dated hardware.

The point I was making was about registering new EKs/certs into your set of trusted servers. While you can tell the TPMs apart from each other, knowing the EK/cert belongs to your hardware's TPM vs someone else's is the tricky part.

[mike_hearn]

TPMs were moved into the Northbridge (I think) many years ago, at least on Intel systems.

PC hardware still isn't tamper resistant though. Memory may be encrypted but its contents can be tampered with in other ways. Only SGX made a serious attempt to be tamper resistant, although Intel eventually sacrificed that to boost performance.

[UltraSane]

Newer AMD CPUs have TPMs in them.