Introducing zkAPI: private usage credits for any API

tl;dr: zkAPI lets you pay for a metered API without being known. Deposit credits into an Ethereum vault once, then authorize bounded usage with zero-knowledge proofs instead of an identity. The provider sees the requests, and the payment layer sees the spend. Neither learns the link between them.

The Open Anonymity Project built it with the Ethereum Foundation, and it runs on Ethereum Mainnet today.

The problem

Every AI API call today carries an identity. Your API key points to an account, the account to a payment method, and every prompt you send joins the record attached to both. The provider can connect years of your usage into a single profile.

Prompts are personal. People ask AI models about their health, their finances, their doubts. Under the current model, using AI means handing a running transcript of your thinking to whoever holds the billing relationship. The alternatives were poor: pay per request onchain, which is slow, expensive, and traceable by anyone, or trust a middleman not to look.

The idea

zkAPI separates payment from identity. You deposit credits (ETH, USDC, etc.) into a vault contract on Ethereum, one ordinary transaction. From then on, your balance exists as a private note: digital cash that only you can spend and that nobody can trace back to the deposit.