Changed TPM2 attestation statement from TPM2_Quote to TPM2_Certify, etc. #91
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| The uniquely identifying TPM2 key is the Endorsement Key (the EK). As this is a privacy | ||
| sensitive key, the EK is not directly used to attest to any TPM2 asset. Instead, | ||
| the EK is used by an Attestation CA to create an Attestation Key (the AK). The AK is |
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Hello! 👋🏻 Great write-up! I was reading through and got a bit confused by this line, specifically by the EK is used by an Attestation CA to create an Attestation Key. My understanding was that the EK is used to assure a 3rd party (in this case the Privacy CA / Attestation CA) that the AK is in the same TPM as the EK, not for the CA to issue the AK. Am I getting this wrong?
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I think we are saying the same thing. The Attestation CA is just a special CA that uses the TPM protocols (including the EK) to prove the AK is in the same TPM (and has the expected attributes). The Attestation CA then issues a certificate for the AK. Since the AK is a signing key (the EK is a decryption key so the protocol is a bit awkward and non-standard - again, this is one of the reasons we use the term Attestation CA because it acts as a non-standard CA) it is easier to get a signed statement about the properties of a "user key". Defining that signed statement is the point of this effort.
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Agree, but I don't see how that maps to used by an Attestation CA to create an Attestation Key - perhaps used by an Attestation CA to create an Attestation Key certificate is clearer?
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Ha, you are correct. Authors sometimes miss the subtitle wording and when I read ...create and Attestation Key... I meant what you said. A subtle but very important difference. Thanks for pointing this out.
Otherwise the ref to DICE is not resolved
fix table rendering
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I don't have push permissions on Monty's fork, so I am merging into a side branch, I'll do a few fixes, then merge into main. |
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