Ethereum Foundation Unveils zkAPI for Anonymous AI Payments

The Ethereum Foundation has introduced a new system called zkAPI, which allows users to make anonymous payments for AI models and metered APIs. This is a response to the current system, where users are forced to associate their credit card or API keys with every request, exposing their prompt history to infrastructure providers.

zkAPI technology separates payments from user identity by making the spending authorization local using cryptographic notes. The process starts with a standardized transaction where a user deposits funds into a vault contract on Ethereum, which becomes purely digital money.

The authorization process is conducted entirely on the client side, and a zero-knowledge proof is created locally to prove that the transaction falls under the private note without disclosing the state. The system also employs a distinctive serial number, known as a nullifier, to secure the spending process.

Ken Liu, a Stanford computer science PhD candidate, said that zkAPI is 'a generalization of OA unlinkable inference that also abstracts payments away.'

The development could become particularly relevant as AI applications increasingly rely on paid inference and metered services. Instead of requiring users to maintain accounts with individual AI providers, zkAPI creates a payment layer that can potentially allow applications to pay for usage without exposing the identity behind each request.