The Ethereum Foundation has activated zkAPI on the Ethereum mainnet, a technology that allows anonymous payment of API fees for AI services. CoinPost, a blockchain media outlet, reported on Oct. 2 that the technology was built jointly with the Open Anonymity Project, which develops privacy technology.

Users can pre-deposit ETH or USDC into a deposit smart contract. They can then make payments without disclosing transaction details, using zero-knowledge proofs to show only that they hold a balance. The server checks only whether the proof is valid and then issues an API key that is valid for a short time.

Under this structure, both the payment layer and the API provider find it difficult to link billing details with a user's identity. Existing API payments have been cited as having a limitation in that usage records are linked to payment accounts, allowing AI service input content to accumulate on the provider side.

zkAPI is based on a design draft written jointly by researcher Davide Crapis (다비데 크라피스) and Ethereum co-founder Vitalik Buterin (비탈릭 부테린). The design draft was disclosed on the Ethereum Research Forum.

Some limitations remain. If a user continues to connect from the same fixed IP address, a gateway may be able to correlate request patterns. Use of Tor, which uses a new circuit for each session, is recommended for users who need greater anonymity.

If the same personal information, writing style or past conversation history is repeatedly revealed, an AI provider may also be able to link multiple sessions. On the other hand, the closer interactions are to one-off exchanges, the higher the anonymity becomes, but it becomes harder to obtain answers that reflect past context.

The development team presented a mitigation approach in which a model in a local environment or a confidential computing environment writes a draft instead of relying on manual input.