The Ethereum Foundation and the Open Anonymity Project put zkAPI live on Ethereum mainnet on October 1, letting people pay for AI services without linking their identity to their prompts. Users deposit funds into a vault contract and spend through zero-knowledge proofs, so the AI provider sees the request but never the payer.
Payment separated from identity
The Ethereum Foundation has put zkAPI live on Ethereum's main network, a system that lets people pay for AI services without tying their identity to what they ask. The foundation described the design as separating payment from identity, turning a deposit into a vault contract into spendable credit that cannot be traced back to the depositor.
According to the Ethereum Foundation: "Prompts are personal. People ask AI models about their health, their finances, their doubts." The foundation built the system with the Open Anonymity Project, which also launched OA Chat, a browser-based private chatbot that needs no installation.
How the proof mechanism works
Users first deposit ETH into the ZkAPIVault smart contract on Ethereum mainnet, where the Open Anonymity Project explained the deposit becomes a commitment through a Merkle tree while the spending balance stays as a private note on the user's device.
At the start of a session, the browser generates a zero-knowledge proof that shows the user has enough funds without revealing which deposit is being spent or who the user is. The server checks the proof and returns a temporary API key capped at a dollar amount, which lives only in the device's memory. Requests then go to the AI provider with that key and nothing else, no name and no payment details attached.
When the key expires, the provider issues a signed usage receipt, and a one-way nullifier prevents the same funds from being spent twice, according to CryptoPotato's description of the settlement step. The provider sees what was asked; the payment layer sees what was spent. Neither side can link the two.
Built on an earlier research proposal
The design follows a proposal Davide Crapis and Vitalik Buterin posted on Ethereum Research in February. Crapis leads the foundation's dAI team, which aims to make Ethereum the preferred settlement layer for AI agents. The project's documentation points to OpenRouter as the AI provider behind the keys, and the repository labels the protocol experimental without listing a formal audit.
Still, the privacy is partial. AI providers can read the content users submit and, per CryptoPotato, may connect sessions through repeated details even though payment records stay separate from the prompts.
Sources: Decrypt, CryptoPotato
Trading involves risk.
Risk Disclaimer
