Ethereum Foundation Launches zkAPI for Private API Payments

What zkAPI Does

The Ethereum Foundation and Open Anonymity Project launched zkAPI on Ethereum mainnet on October 1. The tool lets users deposit credits into a prepaid account and prove that a later API request is paid for without disclosing their identity to the payment server. The system separates the billing layer from the request layer, so the payment processor and the API provider operate independently.

Privacy Boundaries

While zkAPI obscures the payer's identity from payment servers, it does not conceal the actual prompt or request content from the AI provider. The model receives and processes the full prompt text; only the payment metadata remains decoupled from the user's identity. According to reporting, AI providers can potentially identify sessions through repeated request details, even without explicit identity binding. OA Chat, a chat interface, has integrated support for zkAPI's prepaid mechanism.

Technical Mechanism

The separation of identity from payment is enforced through zero-knowledge proofs. A user proves to the payment server that they hold valid credits without revealing who they are; separately, the API provider confirms the request was prepaid without learning the requester's identity. This architecture allows both parties to operate trustlessly without exchanging direct personal information, though session correlation remains possible through request patterns.