Intent to Ship: Private Aggregation API: client-side contribution merging

[Alex Turner]

Contact emails

ale...@chromium.org

Explainer

https://github.com/patcg-individual-drafts/private-aggregation-api/pull/135

Specification

https://github.com/patcg-individual-drafts/private-aggregation-api/pull/136

Summary

Modifies the Private Aggregation API to merge histogram contributions with the same bucket and filtering ID before embedding in the aggregatable report's encrypted payload. Private Aggregation imposes a limit on the number of contributions that can be embedded in a single aggregatable report, with any additional contributions being dropped. By merging together contributions where possible, we can get additional utility out of the limit. Note that, ignoring the dropping of excess contributions, merging these sorts of contributions should not have any impact on the final outputs (i.e. summary reports).

Blink component

Blink>PrivateAggregation

TAG review

https://github.com/w3ctag/design-reviews/issues/846 (We have not requested a signal for these changes specifically.)

TAG review status

Pending

Risks

Interoperability and Compatibility

None

Gecko: No signal (https://github.com/mozilla/standards-positions/issues/805) We have not requested a signal for this change specifically. The Gecko position on Shared Storage (one of the ways Private Aggregation is exposed) is negative.

WebKit: No signal (https://github.com/WebKit/standards-positions/issues/189) We have not requested a signal for this change specifically.

Web developers: Positive (https://github.com/patcg-individual-drafts/private-aggregation-api/issues/81)

Other signals:

WebView application risks

Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?

None

Debuggability

No new debug capabilities beyond the existing internals page (chrome://private-aggregation-internals) and temporary debug mode. These capabilities will reflect the merged contributions.

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?

All but WebView

Is this feature fully tested by web-platform-tests?

Yes

Flag name on chrome://flags

None

Finch feature name

PrivateAggregationApiContributionMerging

Requires code in //chrome?

False

Tracking bug

https://crbug.com/349980058

Launch bug

https://launch.corp.google.com/launch/4333118

Estimated milestones

Shipping on desktop	129
Shipping on Android	129

Anticipated spec changes

None

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5094168719523840?gate=5075771428438016

This intent message was generated by Chrome Platform Status.

[Vladimir Levin]

This looks like a fairly minor improvement to the API. It seems like the change would allow more contributions without increasing performance concerns. Please let me know if there are any subtleties that I may have missed.

LGTM1

Thanks,

Vlad

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[Yoav Weiss (@Shopify)]

LGTM2

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[Chris Harrelson]

LGTM3

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