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New revelations from the Snowden archive surface
(www.computerweekly.com)
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this post was submitted on 19 Sep 2023
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A discrete TPM has a separate manufacturer. The AMD fTPM is made by AMD, and they have already explained the issue.
https://en.m.wikipedia.org/wiki/AMD_Platform_Security_Processor
Yes, exactly. It has similar concerns to Intel ME (and its fTPM). “I wonder who the fTPM manufacturer is” makes no sense.
Then who makes the coprocessor that is inserted into the die?
Looking into more details of the boot process, it seems like the UEFI manufacturers such as AMI or Phoenix might be the best place to insert a pre-OS boot back door. The PSP (CCP) is just what is used to bootstrap before this step in the process.
https://www.igorslab.de/en/inside-amd-bios-what-is-really-hidden-behind-agesa-the-psp-platform-security-processor-and-the-numbers-of-combo-pi/
AMD, obviously, they're not going to let anyone mess with their lithography masks. With IP bought from ARM, to wit: It's a Cortex A5, which is a bog-standard block of IP if you need something better than a microcontroller but not really beefy either. Or you could say that TSMC makes them, just as the rest of the silicon.
(AMD also has an ARM architecture license and thus the right to design its own ARM cores but a) those were designed to be in a completely different performance class (application server) and b) they never made it to market. They're now probably tinkering on RISC-V in the background in their eternal quest to not have Intel fused to their hip by x86).