Ethereum Foundation puts zkAPI privacy payments on mainnet

The Ethereum Foundation and Open Anonymity Project put zkAPI live on Ethereum mainnet on Oct. 1, letting users pay for metered AI services without linking requests to their billing identity, according to the Foundation’s launch announcement. The system uses zero-knowledge proofs to separate payment from the prompts sent to a model provider.

How does zkAPI separate payments from prompts?

Users deposit ETH, USDC or other credits into an Ethereum vault, then keep the balance as a private note. Software on the user’s device generates a proof that the note covers a payment without identifying the deposit or user, the Foundation said.

The zkAPI server checks the proof and issues a short-lived API key with a spending cap. Prompts go directly from the user’s device to the AI provider; after the key expires, the server deducts actual usage from the private balance. One authorization can cover a session of requests.

Unchained’s report says the Foundation describes the project as experimental. It also reports that the system’s client supports standard OpenAI and Ollama interfaces, and that Open Anonymity added zkAPI as a payment option in its OA Chat app.

What information can providers still see?

AI providers still see prompt contents and network metadata, including IP addresses, the Foundation said. Repeated personal details or writing style can also link separate sessions, so zkAPI hides the payment connection rather than providing network or content anonymity.

The Foundation says the same setup can support other metered services, including blockchain queries, image generation, VPN bandwidth and machine-to-machine payments. The vault is live on mainnet; providers that integrate zkAPI will need to accept proofs and settle signed usage receipts, while retaining their existing pricing and rate limits.

References

• Foundation’s launch announcement — blog.ethereum.org
• Unchained’s report — unchainedcrypto.com