The Ethereum Foundation has launched zkAPI on Ethereum’s mainnet, a new system designed to enable private payments for artificial intelligence (AI) services. This development aims to address growing privacy concerns by decoupling users’ identities from their AI queries, according to the Ethereum Foundation’s announcement.
zkAPI, developed in collaboration with the Open Anonymity Project, allows users to pay for AI services using cryptocurrencies like ETH and USDC without linking their personal identity to their AI interactions. Users deposit funds into a vault contract on the Ethereum network, which then functions as private digital cash. A zero-knowledge proof is employed to verify that sufficient funds are available without revealing specific transaction details. Subsequently, a temporary API key is issued to the user’s device, granting access to AI services. Usage is charged based on actual consumption after the key expires, with AI providers and payment processors having separate visibility into the query and the spending, respectively, preventing them from linking the two.
Addressing AI Privacy Concerns
The Ethereum Foundation argued that current AI usage models compromise user privacy by linking queries to billing relationships. “Prompts are personal. People ask AI models about their health, their finances, their doubts. Under the current model, using AI means handing a running transcript of your thinking to whoever holds the billing relationship,” the Ethereum Foundation stated. zkAPI aims to resolve this by making “your balance exist as a private note: digital cash that only you can spend and that nobody can trace back to the deposit.”
The system works with OpenRouter, a service that provides access to numerous AI models through a single connection. The project’s documentation indicates that any application compatible with the OpenAI format can integrate with zkAPI by pointing to a local address. The temporary API keys are capped at a specific dollar amount and exist only in the device’s memory, expiring after use.
Origins and Broader Context
The concept behind zkAPI originated from a proposal by Davide Crapis and Vitalik Buterin on Ethereum Research in February. Crapis, who leads the Ethereum Foundation’s dAI team, which focuses on making Ethereum a preferred settlement and coordination layer for AI, had previously suggested Ethereum’s potential as infrastructure for software agents. In August 2025, Crapis and Marco De Rossi proposed the ERC-8004 standard, a framework for AI agents to find each other, verify identity, and transact. Crapis has predicted that machine-generated Ethereum traffic could constitute the majority within three to five years.
Vitalik Buterin has also been active in outlining Ethereum’s role in AI. On February 10, he presented an Ethereum-AI roadmap that included zero-knowledge payments for private API use. In April, he discussed the alternative of running open-source AI models locally on personal hardware, such as an Nvidia 5090 graphics card, to keep data private. zkAPI addresses scenarios where prompts still need to be sent to external servers.
The concern over AI privacy is underscored by recent events, such as a federal court order in May 2025 for OpenAI to preserve its output logs, including deleted chats, in response to a lawsuit by The New York Times and other publishers. The potential applications for zkAPI extend beyond AI services, with the possibility of covering other metered services like blockchain data queries, image and video generation, and VPNs.
Experimental Status
It is important to note that the zkAPI protocol is labeled as experimental in its repository, and a formal audit has not been listed. Providers integrating with zkAPI would need to accept a proof instead of a traditional API key and settle signed usage receipts.
Why This Matters
The materials describe a narrow update: zkAPI, developed with the Open Anonymity Project, allows users to pay for AI services using cryptocurrency (ETH, USDC) without linking their identity to their AI queries. The formal audit status of the zkAPI protocol.
