Ethereum Foundation Unveils zkAPI for Private AI Payments
The Ethereum Foundation has introduced a new payment system called zkAPI, which allows users to pay for AI and metered API services without revealing their billing identity. The system, launched on October 1, uses zero-knowledge proofs to authorize short-lived API keys without disclosing which deposit funded the request.
The design of zkAPI originates from a February proposal by Davide Crapis and Vitalik Buterin, and uses a combination of cryptographic techniques, including Groth16 proofs, Poseidon hashes, and a 32-level Merkle tree. The system provides payment privacy, but not full anonymity, as providers can still see prompts, and IP addresses, timing, and content can link sessions.
The launch of zkAPI addresses a structural feature of commercial AI APIs, where a key points to an account, the account points to a payment method, and every prompt joins the record attached to both. The system replaces this persistent billing identity with a private note, allowing users to deposit funds into a vault contract and then authorize metered API sessions without the payment server ever learning which deposit is backing the request.