Ethereum Foundation puts private API payment system zkAPI on mainnet

The Ethereum Foundation and Open Anonymity Project launched zkAPI on Ethereum mainnet on Oct. 1, letting users pay for AI and other metered APIs without linking their billing identity to requests, according to the Ethereum Foundation’s launch post. The system uses zero-knowledge proofs to separate payment records from API usage.

How does zkAPI separate payments from API use?

Users deposit credits, including ETH or USDC, into an Ethereum vault in a single transaction, then use private notes to authorize spending. Software on the user’s device generates a proof that the balance covers the requested use without disclosing which deposit paid.

The zkAPI server checks the proof and issues a short-lived API key with a spending cap. The user’s prompts go directly to the AI provider in this mode; after the key expires, a signed receipt records usage and the server deducts that amount from the private balance, the foundation says.

What information can providers still see?

AI providers still see prompts and responses, and zkAPI does not hide users’ IP addresses or request timing. The foundation says providers may be able to link sessions through network patterns, reused personal details or conversation history.

The mainnet launch follows a proposal for zero-knowledge API usage credits by Ethereum Foundation researcher Davide Crapis and Ethereum co-founder Vitalik Buterin. Cointelegraph reported on the launch as the proposal’s move into a working mainnet system.

What needs to happen for API providers to use it?

Providers must accept payment proofs instead of API keys and settle signed usage receipts, according to the foundation. It says pricing, rate limits and infrastructure can stay as they are; the system is live on mainnet, with a local client, browser SDK and browser-based AI chat available.

Source material

• Ethereum Foundation’s launch post — blog.ethereum.org
• reported on the launch — cointelegraph.com