Ethereum's zkAPI: Separating Payment from Identity in AI Services
The Ethereum Foundation and Open Anonymity Project have launched zkAPI, a system that separates payment from identity in AI and other metered services. This is made possible by zero-knowledge proofs and disposable API keys, which prevent the AI provider from knowing who is making the request. However, there is a catch: the AI still sees the prompt, and anonymity can unravel elsewhere.
zkAPI uses a normal Ethereum transaction to deposit credits into a vault contract. The funds are then represented by a private note that can be spent without identifying which original deposit supplied the money. A zero-knowledge proof is produced, showing that the funded note can cover the requested spending and hasn't already been spent. The server verifies the statement without learning which note belongs to the user.
After payment authorization, a fresh, short-lived API key with a dollar cap is created. This key lives only in the user's device memory, and the prompt heads directly to the AI provider. The provider records the amount actually consumed in a signed usage receipt, and zkAPI deducts that amount from the user's private note.
The protocol's repository labels zkAPI experimental, and the Foundation is candid about another problem: the AI provider still receives prompts and responses, and network information can betray the person on the other end. The Foundation points users seeking stronger network anonymity toward Tor and fresh circuits for separate sessions.