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Explainer https://github.com/WICG/turtledove/pull/1322 Specification https://github.com/WICG/turtledove/pull/1313 Summary Additional bids are a feature of the Protected Audience auction that provide buyers with a way to include server-constructed contextual bids in the auction, which allows negative targeting of those bids. We've identified a potential privacy risk with the current implementation, as well as a potential solution that addresses that risk. Additional bids come from buyers, but are transported to the auction by the auction's seller. To prevent replay of additional bids, additional bids rely on an auction nonce — a unique number created by and used by the browser to uniquely identify that auction. However, this introduces a privacy risk, in that all buyers see the same auction nonce, and could use that auction nonce as a key to join distinct bid requests for an auction. This proposal allows sellers to introduce an additional nonce that gets combined with the browser-provided one so that buyers see different combined nonces across bid requests, preventing the joining of bid requests. The combined nonce is generated through a one-way hash (SHA-256) to prevent the construction of a combined nonce that matches a previous combined nonce, which could otherwise be used to facilitate the replay of an additional bid. Blink component Blink>InterestGroups <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EInterestGroups> TAG review For Protected Audience: https://github.com/w3ctag/design-reviews/issues/723 TAG review status Completed for Protected Audience, resolved unsatisfied. Risks Interoperability and Compatibility Optional new functionality that does not break existing use. Gecko & WebKit: For Protected Audiences in general - Negative from Mozilla <https://github.com/mozilla/standards-positions/issues/770#issuecomment-2432124085>. No signal from Webkit <https://github.com/WebKit/standards-positions/issues/158#issuecomment-2432121278> . Edge: Edge is running an Origin Trial of the Ad Selection API <https://github.com/WICG/privacy-preserving-ads/blob/main/README.md> which shares a Web API and services protocol with Protected Audience. Web developers: Requested by ad tech in GitHub issue #1198 <https://github.com/WICG/turtledove/issues/1198>. Debuggability Ad-Auction-Additional-Bid response headers are visible in the DevTools Network tab, and each can be trivially decoded into an auction nonce, a seller nonce, and a base-64 encoded signed additional bid. Errors encountered while decoding and parsing the signed additional bid are presented in the DevTools console. Additional bids are debuggable via DevTools debugging of Protected Audience scoring scripts. Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)? It will be supported on all platforms that support Protected Audience, so all but WebView. Is this feature fully tested by web-platform-tests <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md> ? Yes <https://chromium-review.googlesource.com/c/chromium/src/+/5979020> Flag name on chrome://flags None Finch feature name FledgeSellerNonce Requires code in //chrome? False Estimated milestones Shipping on desktop and Android in M132. Anticipated spec changes None Link to entry on the Chrome Platform Status https://chromestatus.com/feature/5081571282124800 This intent message was generated by Chrome Platform Status <https://chromestatus.com/>. -- You received this message because you are subscribed to the Google Groups "blink-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to blink-dev+unsubscr...@chromium.org. To view this discussion visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CANHsO6stZ5OtCo3xy127pz_9w7V_NJjx2ZvfzP%2BnJowRC8cmzg%40mail.gmail.com.
