The Ethereum Foundation has introduced zkAPI, a system designed to enable anonymous payments for AI models and metered APIs. Developed in collaboration with the Open Anonymity Project, the protocol is currently live on the Ethereum mainnet.
To utilize the service, users deposit tokens like ETH or USDC into a vault contract. The system generates zero-knowledge proofs to verify funds without disclosing the user's identity. A temporary API key is then issued for service access.
The protocol uses a nullifier mechanism to prevent double-spending of balances. It is compatible with existing tools, including OpenAI and Ollama APIs, by allowing users to point applications to a local host.
The system supports use cases such as AI chat, image generation, and blockchain RPC queries. However, the Foundation notes that zkAPI does not provide network-level anonymity, suggesting Tor for users seeking additional privacy.
The project is based on the ZK API Usage Credits design, co-authored by Vitalik Buterin and Davide Crapis. It is part of the work of the dAI team, which was established by the Foundation in September 2025.
