Event level win reporting with B & A services

[siddhash1]

Based on the Bidding and Auction services fledge docs, this is my understanding of the event level win reporting flow so far:

ReportWin() and ReportResult() would be called in the auction service. They would encode the reporting information into reporting urls for the buyer and seller respectively. These would be returned to the client (browser) as part of AuctionResult as WinReportingUrls. The client would automatically ping the win reporting urls immediately after the ad is rendered, and register ad beacons, if any.

1. Is this understanding correct?
2. I see that we do not have the browserSignals argument to the ReportWin and ReportResult that we had with client-side auctions as described here. Does that mean we do not include that information in the reporting now? I see there's a new reporting_metadata argument in the server-side but I'm unclear what information is contained in that. The browserSignalsincluded the winning interestGroupName in the client-side version, with an additional k-anonymity constraint on the tuple of interest group owner, name, bidding script URL and ad creative URL. Depending on whether or not this information is included in the server-side auction flow, I'm curious if the k-anon check is still required and if yes, where it would occur.

[JensenPaul]

@chatterjee-priyanka does B&A pass browserSgnals to reportWin() and reportResult()?

[chatterjee-priyanka]

Thanks @siddhash1 and @JensenPaul. Apologies about the super delay.

1. This is correct. You may also refer to the event level reporting explainer- https://github.com/privacysandbox/protected-auction-services-docs/blob/main/bidding_auction_event_level_reporting.md

2. reportingMetadata arg contains information that browserSignal has for on-device reporting url generation; since the signal is not constructed on browser but in B&A, we had to name the arg sellerReportingMetadata for reportResult and buyerReportingMetadata for reportWin respectively.

• For sellerReportingMetadata, refer here- https://github.com/privacysandbox/protected-auction-services-docs/blob/main/bidding_auction_event_level_reporting.md#the-reportresult-specification.
• For buyerReportingMetadata refer here- https://github.com/privacysandbox/protected-auction-services-docs/blob/main/bidding_auction_event_level_reporting.md#the-reportwin-specification
• This explainer would be updated to incorporate reportingId information.
• The K-Anon check would happen in Auction server and K-Anonymity constraint on the tuple would be applied similarly as well. We plan to publish a K-Anonymity explainer in https://github.com/privacysandbox/protected-auction-services-docs by end of July 2024.

One request, if the questions are B&A specific, we have a WICG Protected Auction discussion repo now. You may file issues there directly, so that I don't miss.