Re:TPM GPIO fail: How bad OEM firmware ruins Intel TPM security
by logical_person on Friday June 07, 2024 @12:06AM
(#40605232)
before the popularity of ARM SoCs that contain everything on-die there were much fewer choices for vertically integrated devices. it's a different segment.
if you look at apple's vertically integrated devices, they chose a cryptography coprocessor that was not on die originally. with a key accessible only by both pieces of silicon's trusted execution environments, rather than the operating system directly, encrypted comms are established in a similar fashion as the TPM2.0 proposal.
But there are multiple caveats: - How do you hide the secret so that only "legitimate" operating systems can use it for establishing their sessions and not "Mate's bootleg totally not malware live USB"? - And unfortunately current CPUs don't implement this. - Additionally don't be so smug to think you need to decap a CPU to extract on-die secrets. Fault injection attacks are very effective and hard to defend against.
I agree the security of this can somewhat be somewhat improved, but if you are building a custom CPU anyhow, you might as well move the TPM on-die and avoid this problem entirely.