Contact emails

pauljen...@chromium.org


Explainer

https://github.com/WICG/turtledove/blob/main/PA_real_time_monitoring.md


Specification

https://github.com/WICG/turtledove/pull/1212


Summary

The goal of real-time monitoring is to get Protected Audience API auction
monitoring data to the buyer and seller as quickly as possible (e.g. < 5
mins). The primary use-case we are trying to capture with this reporting
surface, the Protected Audience Real Time Monitoring (RTM) API, is rapid
error detection i.e. detecting quickly whether there are major problems
with unexpected behavior in generateBid(), scoreAd(), or loading of bidding
or scoring scripts or trusted signals. To offer reduced latency over other
reporting mechanisms like the Private Aggregation API, the RTM API uses the
local differentially private RAPPOR algorithm with an epsilon of one.  The
reduced latency is traded off for a limited number of histogram buckets and
significant noise.


Blink component

Blink>InterestGroups
<https://issues.chromium.org/issues?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.


RisksPrivacy

At the epsilon we are proposing (đťś– = 1), the information leaked is limited
to approximately 0.18 bits per auction. This makes it very difficult for a
bad actor to gain any meaningful user identifying information from an
auction using this API.

While the tight privacy parameters provide strong protections, there are
two privacy considerations of note:

   -

   It reveals a small amount of information from scoreAd and generateBid to
   sellers and bidders, respectively. These contents are protected by the
   locally differentially private RAPPOR algorithm. The scope of this risk can
   be measured with the privacy loss epsilon parameter. This risk could be
   magnified by a bad actor running many auctions solely for the purpose of
   collecting more information from a publisher page. We mitigate this risk by
   bounding the number of contributions that this API will send to an adtech
   from a page in a given period of time for each browser.
   -

   It reveals to the ad tech the fact that it had an interest group present
   on the device. This is mitigated by the fact that the reports are sent to a
   fixed path and include only heavily noised signals. We also considered
   sending reports to all eligible auction participants for a given auction
   (i.e. all those present in interestGroupBuyers, even if they do not have
   interest groups), but this will result in an overwhelming number of reports
   sent.

We plan to address both these considerations in future work
<https://github.com/WICG/turtledove/blob/main/PA_real_time_monitoring.md#limitations-and-future-work>
.
Interoperability and Compatibility

This feature represents optional new behavior that shouldn’t break existing
usage.


Gecko & WebKit: No signal on parent proposal, Protected Audience.  Asked in
the Mozilla forum here
<https://github.com/mozilla/standards-positions/issues/770>, and in the
Webkit forum here <https://github.com/WebKit/standards-positions/issues/158>
.


Edge: Edge has announced plans to support the Ad Selection API
<https://github.com/WICG/privacy-preserving-ads/blob/main/README.md> which
shares much of its API surface with Protected Audience.


Web developers: Interest from 5 companies on GitHub issue
<https://github.com/WICG/turtledove/issues/430> and significant interest on
WICG call discussion
<https://github.com/WICG/turtledove/blob/main/meetings/2024-02-28-FLEDGE-call-minutes.md?plain=1#L120>
.


Debuggability

RTM API network requests will show up in the Chrome Developer Tools network
panel. Calls to the RTM API from Protected Audience bidding and scoring
scripts should also be debuggable with Chrome Developer Tools.


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>
?

We’ve landed some
<https://github.com/web-platform-tests/wpt/blob/f118165cd650448765d2e0efd3d7ee71f1e15e4f/fledge/tentative/auction-config.https.window.js#L510>
but plan to land more web-platform-tests shortly.


Flag name on chrome://flags

None


Finch feature name

RealTimeReporting


Requires code in //chrome?

False


Estimated milestones

Shipping on desktop and Android in M128.

Anticipated spec changes

None


Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5200293940428800


This intent message was generated by Chrome Platform Status
<https://chromestatus.com/>.

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