Ethereum Foundation Introduces zkAPI for Private API Payments

The Ethereum Foundation has introduced zkAPI, a system that uses Ethereum credits for private API payments on the Ethereum mainnet. This system allows users to fund metered APIs without revealing their identity, but it does not hide prompts, responses, or network metadata.

The system works by depositing assets such as ETH or USDC into a vault contract on Ethereum. The transaction is ordinary, but the resulting balance exists as a private note that cannot be traced back to the deposit.

When a user makes a request, software on their device creates a zero-knowledge proof showing that the user funded the session without exposing the deposit transaction. The server checks the proof without learning the user's identity or the original deposit. One proof can authorize a single request or an entire session.

The server then creates a short-lived API key capped in dollars, which stays in the user's device's memory. Once it expires, the AI provider records actual usage in a signed receipt, and the server deducts that amount from the user's private balance. The final charge is based on metered use, not the full amount reserved at the start.