Intent to Ship: Protected Audience features: recency, rounding bids & scores
Paul Jensen
Contact emails
Explainer
Specification
https://github.com/WICG/turtledove/pull/711
https://github.com/WICG/turtledove/pull/636
Summary
This I2S covers two features extending Protected Audience:
Recency:
The “recency” signal for Protected Audience interest groups indicates how long ago the user was joined to an interest group, which can be a useful signal when calculating an ad auction bid (e.g. recently expressed interest likely indicates more interest). Previously we provided this signal in a strictly bucketed and noised form to buyers’ win reporting function, reportWin(). This change additionally exposes this signal to the buyers’ bidding function, generateBid(). It can be provided without bucketing or noising to generateBid() like other signals available in that function. In fact, Protected Audience already allows developers to calculate this signal (e.g. by storing join time in the interest group), but developers have asked (see “Web Developers” section below) to have the browser supply it to generateBid() to ensure it’s calculated identically to the value supplied to the reporting function, so that models training on the reported data are compatible with bidding.
Rounding bids and scores:
In Protected Audience, the bid price and desirability score pass from functions that have access to cross-site data (generateBid() and scoreAd()) to the reporting worklets that have access to first party data (reportWin() and reportResult()), so to prevent event-level win reports from facilitating cross-site identity joins, we need to limit this data as much as possible. This change limits the information in the bid price and desirability score by rounding them from 64-bit floating-point numbers to 16-bit floating point numbers. Previously these numbers were not rounded.
Blink component
TAG review
The parent proposal, Protected Audience, is still pending: https://github.com/w3ctag/design-reviews/issues/723
TAG review status
Pending
Risks
Interoperability and Compatibility
Recency: This is unlikely to break existing sites as it’s only adding a new field to an object the browser provides to Protected Audience bidding and scoring scripts.
Rounding: This is unlikely to break existing sites as it’s only clearing some of the less significant bits of the bid and score values, while not changing the most significant bits or where the values flow from and to.
Gecko & WebKit: No signal on parent proposal, Protected Audience. Asked here and here.
Web developers:
Recency: Adtechs asked for the recency feature here as part of the larger ask.
Rounding: This has been part of Protected Audience’s plan to accomplish our privacy goals for some time. We haven’t heard significant resistance.
Debuggability
These features affect values provided to Protected Audience scripts (generateBid(), reportResult(), reportWin()) which are debuggable via Chrome DevTools.
Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, 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?
These are in progress and hope to land before M116 stable release.
Finch feature name
FledgeRounding
Requires code in //chrome?
False
Estimated milestones
Shipping on desktop and Android in M116.
Anticipated spec changes
None related to these two features.
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/5084137479733248
This intent message was generated by Chrome Platform Status.
Chris Harrelson
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Mike Taylor
LGTM2
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Alex Russell
LGTM1
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