Ethereum's zkAPI has been launched on the mainnet, turning the previous proposals regarding zero-knowledge API payments into a practical implementation that can be used for private, prepaid access.

On Thursday, the Ethereum Foundation announced that zkAPI has been launched on the Ethereum mainnet. This system was built with the participation of Open Anonymity Project and is designed to allow users to pay for AI and other API services without exposing their billing identities.

According to the statement in a post by dAI of the Ethereum Foundation and AI, the coordinator Vittorio Rivabella, users first deposit funds into the Ethereum treasury and then use zero-knowledge proofs to demonstrate that they have sufficient credit to make a API request, without having to reveal which specific deposit those funds belong to.

One direct use of this system is to pay for the usage fees of AI without linking the payment to the user's identity. zkAPI issues short-term API keys with preset expenditure limits. Prompt words are sent directly to the provider of AI, while the usage fees are settled separately through the payment layer. This project has also released a local client and a software development toolkit, as well as a browser-based AI chat implementation.

This launch incorporates the zero-knowledge proof-based quota scheme API proposed in February by Ethereum Foundation researcher Davide Crapis and Ethereum co-founder Vitalik Buterin. The new release has turned this design into a functional mainnet implementation.

When this concept was proposed, it was seen as a way to provide private, prepaid access for AI and other pay-as-you-go API. However, zkAPI does not hide the content of prompts or network metadata from service providers, which means that users may still be associated between different sessions through the IP address, timestamps, or information contained in requests.