Ethereum Foundation Launches zkAPI for Private AI Payments on Ethereum

The Ethereum Foundation and the Open Anonymity Project launched zkAPI on Ethereum mainnet, a payment system that lets people use metered AI services without giving providers their billing identity.

To fund usage, users place Ether (ETH), USDC or another supported token in a vault on Ethereum. Software on their devices generates zero-knowledge proofs showing funds are available without revealing which deposit backs a payment.

A server uses each proof to issue a temporary API key with a spending limit. Users send prompts directly to an AI provider, while a separate payment server checks proofs and deducts charges based on usage.

The AI provider receives prompts but not the payer’s billing identity. The payment server checks proofs without receiving prompt content. The system can also support blockchain queries, image and video generation, VPN bandwidth and payments between AI agents.

The design does not conceal every identifying detail. Providers still receive prompts, which may reveal personal information, writing patterns or reused conversation history. A stable IP address may also help connect requests; routing traffic through Tor can add network privacy.

zkAPI implements a design called “ZK API Usage Credits,” published Feb. 11 by Ethereum Foundation dAI lead Davide Crapis and Ethereum co-founder Vitalik Buterin. The project describes zkAPI as experimental.