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I was just going through TPM Overview and What makes TPM chip Endorsement Key Non-migratable? but it seems like the "trust" is a matter of "trusting" the manufacturer to not be malicious or be negligent in developing the platform.

I didn't really see any way of verifying the trustworthiness in that there is no way to tamper or clone the module especially since we don't control the module maker. Nor would there be a way to prevent the module maker from creating a duplicate TPM with the exact same keys.

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When customers have a need "of "trusting" the manufacturer to not be malicious or be negligent in developing the platform.", manufacturers get those audited and certified by a trusted 3rd party auditor, to declare that the TPM is compliant to a certain standard/certification like Common Criteria or FIPS 140-2. This implies customers trust the 3rd party which do this audit and certification. I think it is possible big customers may themselves do a similar audit regularly on manufacturer by themselves (e.g. every year or 2 year)

https://trustedcomputinggroup.org/resource/pc-client-tpm-certification/ --> talking about Common Criteria certified TPM https://www.microchip.com/en-us/products/security/security-ics/tpm --> talking about FIPS 140-2 certified TPM

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  • So in essence there's no technical way of ensuring trust. Only through certifications. Which then someone may go "who watches the watchmen?" But I think this is the best we can go with. Jul 20, 2022 at 3:51
  • @ArchimedesTrajano Next level. How would you verify trust in the technical program that verifies TPM?
    – doneal24
    Jul 20, 2022 at 13:40
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    "who watches the watchmen?". The one doing the certifications are accredited laboratories, which means they are subjects to regular audit (see csrc.nist.gov/projects/cryptographic-module-validation-program), in the US the accrediting body is NVLAP (nist.gov/nvlap). Basically to ensure you get a malicious certified you need to corrupt manufacturer, laboratory and accrediting body, which is way too many to keep it secret. Better to try to hide it and hope the lab misses it, which is a more likely scenario, plenty of vulns have been found in certified hardware and software. May 11, 2023 at 14:24
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TPM is not about you trusting the manufacturer, it's about the issuer of a license trusting your hardware.

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