Ethereum's zkAPI Brings Private AI Payments to Mainnet

The Ethereum Foundation has launched zkAPI, a payment system that allows users to access metered AI services without revealing their billing identity. This innovation uses zero-knowledge proofs to ensure secure and private transactions on the Ethereum mainnet.

User funds are held in a vault on Ethereum, where software generates these proofs showing available balances without disclosing which deposit backs each payment. The system provides a temporary API key with a spending limit, allowing users to send prompts directly to AI providers while keeping their billing information anonymous.

The AI provider receives the prompt but not the payer's identity, and the payment server checks proofs without accessing the prompt content. This design supports various use cases beyond payments, including blockchain queries, image and video generation, VPN bandwidth, and transactions between AI agents.

While zkAPI does not conceal all identifying details, it still provides a significant level of network privacy. The system's 'ZK API Usage Credits' design was published by Ethereum Foundation dAI lead Davide Crapis and co-founder Vitalik Buterin on February 11. This project is described as experimental.