Ethereum Foundation Unveils zkAPI for Anonymizing AI Model Payments

The Ethereum Foundation has launched zkAPI, a system for paying for AI models and other metered online services without linking usage to the payer. The tool uses zero-knowledge proofs to hide AI prompts from payers on Ethereum mainnet.

Users make a single deposit of crypto, such as ETH or USDC, into a vault contract on Ethereum. A software on their machine generates a zero-knowledge proof showing that some funded balance covers the cost without revealing which one. This proof is then checked by a zkAPI server, and a temporary API key with a dollar cap is issued.

The AI provider receives the prompt with the temporary API key, and the private balance is charged for actual usage once the key expires. Each spend also publishes a one-time identifier that exposes any attempt to reuse a balance.

The foundation said zkAPI does not provide network anonymity, and AI providers can still read what a request contains and see metadata such as a user's IP address.