The Ethereum Foundation and the Open Anonymity Undertaking have introduced a mainnet system on-line that lets individuals pay for metered APIs with out tying these calls to a sturdy billing id.
Introduced on October 1, 2026, by Vittorio Rivabella of the Foundation’s dAI workforce, the design—referred to as zkAPI—is already working on Ethereum and implements an earlier analysis proposal from Davide Crapis and Vitalik Buterin.
Strange API entry right now binds each request to an account.
An API key maps to a consumer, that consumer maps to a payment methodology, and the supplier can assemble years of prompts right into a single profile.
As a result of individuals routinely ask fashions about well being, money, and personal doubts, that association fingers a protracted transcript of thought to whoever holds the billing relationship.
Paying per name instantly on-chain avoids the intermediary however is gradual, expensive, and publicly traceable.
Trusting an middleman to not examine visitors is the opposite widespread compromise.
zkAPI splits the cost relationship from the content material of the request.
A consumer deposits ETH, USDC, or related belongings right into a vault contract in a single peculiar transaction.
From that time the stability exists as a personal observe—successfully digital money that solely the holder can spend and that can’t be traced again to the unique deposit.
When spending is required, software program on the consumer’s personal gadget produces a compact zero-knowledge proof asserting {that a} funded observe covers a bounded quantity of utilization and has not already been spent.
One proof can authorize a single name or a whole session.
The server can affirm the assertion is true with out studying which observe, which deposit, or which individual stands behind it.
On the payment layer, successive requests neither hyperlink to the consumer nor to 1 one other.Two cryptographic mechanisms assist the declare.
Deposits are saved as commitments inside a Merkle tree, so a proof can display {that a} observe belongs among the many legitimate set with out figuring out it.
Every spend additionally publishes a nullifier, a one-way serial quantity derived from the observe’s secret.
Staying contained in the stability retains exercise unlinkable; making an attempt to spend the identical funds twice produces a replica nullifier that reveals solely the double-spend try.
In operation, a small consumer on the consumer’s machine speaks the acquainted API.
It forwards a cost proof—containing neither immediate nor id—to the zkAPI server.
The server checks the proof and points a short-lived key capped in {dollars}, which lives solely in native reminiscence.
Prompts then journey instantly from the gadget to the supplier underneath that key.
When the important thing expires, a signed utilization receipt information precise consumption, and the server deducts that quantity from the non-public observe reasonably than the complete reserved cap.
Neither social gathering can alter the invoice afterward.
A less complicated proxy mode exists through which the server relays visitors, however the popular path retains content material away from the payment middleman fully.
Proofs use Groth16 over the BN254 curve, with Poseidon hashes for commitments and nullifiers, and notes held in a 32-level Merkle tree.
Spend proofs are verified off-chain by the server; the vault contract itself checks equal proofs at deposit, shut, and withdrawal, so customers can exit even when each server vanishes.
Funds subsequently stay underneath the consumer’s management on Ethereum reasonably than in an organization account.
The division of information is express.
The zkAPI server learns {that a} legitimate cost exists and the greenback whole for a session, however not the consumer’s identity, the content material of requests, or which deposit funded them.
The AI supplier sees prompts and responses as a result of it should run the mannequin, but by no means learns who’s paying.
The general public Ethereum chain information deposits, closures, and withdrawals, however not what any stability was spent on.
The identical consumer and contracts can entrance different metered providers—blockchain RPC queries, picture or video jobs, VPN bandwidth, or machine-to-machine duties—hiding the funding hyperlink in every case.
Present purposes want little change: the native consumer exposes commonplace OpenAI– and Ollama-compatible endpoints, so editors and chat instruments can merely level at localhost.
A browser chat interface can also be obtainable.
The protections cease on the cost hyperlink.
Suppliers nonetheless observe request contents and community metadata resembling IP addresses, and so they can try to correlate classes by timing or by recurring private particulars, writing fashion, or dialog historical past inside prompts.
Community anonymity requires a separate layer resembling Tor with a contemporary circuit per session; content material privateness is an extra, still-emerging concern addressed by methods like confidential computing. The protocol is described as being considerably experimental.
