Ways for a device to prove it is genuine without revealing which device it is.
Plain attestation has a privacy cost. If every device signs with its own key, every verifier can recognise the device and follow it. For phones, cars and personal computers, that is tracking.
A privacy certificate authority was the first answer: a trusted third party checks the device and issues it a fresh pseudonym. It works, but the authority sees everything.
Direct Anonymous Attestation (DAA) removed the third party. A device joins a group once, then signs as 'a genuine member of the group'. Verifiers can check the signature without learning which member signed. DAA has been part of the TPM standard since version 1.2.
EPID, Intel's Enhanced Privacy ID, is a related group scheme with revocation. It was the original basis of SGX attestation. Intel has since moved SGX to certificate-based attestation, which is simpler to run and does not hide which platform signed.
The tension remains in every design: verifiers want to revoke one bad device, and users do not want to be recognisable. Android's short-lived attestation certificates and the unlinkability rules for EU wallets are current answers to the same question.
Attested wallets and digital identityAttested devices
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Next fixed date: EU Digital Identity Wallets are due in every member state on 24 December 2026, 42 days from now.