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In term of authentication, I have the impression that to trust an entity it is mandatory to have a Certification Authority involve. Today I stumble upon an article something called Direct Anonymous Attestation is possible to get rid of CA. How is that possible when a verifier holds no information nor a trusted party to crosscheck with and yet able to trust an entity. I am not a math genius, can anyone explain how Direct Anonymous Attestation work in layman terms?

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I briefly went through the paper - and interesting article you found. Though I see some gaps and assumptions. If someone understands it better, please feel free to comment or improve. So - in Layman's terms (how I understood it):

Once a subject could prove its identity, its identity (attributes, certificate) is written in a blockchain ladder (and assumed it is difficult to falsify). The identity proof is not explicitly stated, but control over a domain admin addresses are mentioned several times.

What is not explicitly written (and I consider that as assumed knowledge) what would be the blockchain quorum confirming each transaction. In simple terms (very simplified) - it would need mutiple participant to confirm that the identity is ok. Every blockchain participant would become partial CA.

The idea looks good but I see a few issues (at least what I immediately see, unrelated to the math):

  • it is not related to the paper itself, but more to the blockchain ladder properties. If an organization would be able to take over the blockchain (having more participants, more computing power, ...) the trust would be completely broken. The benefic (and thus incentive) for malitious behaviour would be enormous.

  • current CA issued certificates have legal value in many countries (the CAs are not only used for validating domain names) for authentication and signing. That would not work with schema where institutions are unable to enforce legal control.

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  • $\begingroup$ Not to mention not all identity check is possible without physical presence, perhaps it is only for certain use cases. Regarding to Direct Anonymous Attestation, I am surprise to see it is already adopted by the Trusted Computing Group (TCG) in the latest version of its Trusted Platform Module (TPM) specification wiki and paper, still struggle to understand how it actually work $\endgroup$ – Consy Jul 26 '17 at 15:16

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