v132 · miscellaneous
Protected Audience Auction Nonce Hardening
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 fr
concepts
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PA Nonce Hardening
runAdAuction() nonces require fresh per-call generation. Hardens against replay attacks in multi-seller setups.
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buyer worklet flow
End-to-end: buyer worklet receives auctionNonce, signs additional bids, helper rejects the replay attempt.
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replay attack walkthrough
Pre-v132 attack: capture a signed bid in auction 1, replay it into auction 2 to learn user signals via negative targeting. v132's per-auction nonce kills it. Step-by-step timeline.
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Nonce validator
Generate real 128-bit auction nonces, bind them to simulated auctions (consuming them as single-use), then click "Attempt replay" to see Chrome 132 reject the replayed nonce. An audit table tracks all auctions and their replay status, making the single-use guarantee tangible.
why it shipped
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 fr