Introducing Zero-Knowledge Proofs for Private Web Attestation with Cross/Multi-Vendor Hardware


A few weeks ago we introduced Cryptographic Attestation of Personhood to replace CAPTCHAs with USB security keys, and today we announced additional support for on-device biometric hardware. While doing that work, it occurred to us that hardware attestation, proving identity or other properties of a user with a piece of hardware, could have many wider applications beyond just CAPTCHA alternatives and user authentication via WebAuthn. Really, why should someone have to have an account to prove they exist, when their own trusted device can do so?
Attestation in the WebAuthn standard lets websites know that your security key is authentic. It was designed to have good privacy properties baked into policies that must be followed by device manufacturers. The information your security key sends to websites is indistinguishable from that of myriad other keys. Even so, we wanted to do better. If we’re taking attestation out of authentication, then we need to learn only that your security key is authentic — and we’ve designed a new Zero-Knowledge Proof for the browser to do that.
This is part of our work to improve privacy across the Internet. We’ve yet to put this proof of personhood in production, but you can see Continue reading


