Vitalik Buterin has floated a blockchain-based anonymous payment framework tailored for AI and API services. Users pre-deposit stablecoins and authenticate multiple API calls via zero-knowledge proofs, without revealing their identity or building a traceable usage history.
ZK API Usage Credits: RLN Powers Anonymous Billing
At the core of the proposal are “ZK API usage credits,” built on a zero-knowledge tool called RLN (Rate-Limiting Nullifier). Originally deployed on blockchain as an anti-spam measure that preserves user anonymity, RLN here lets users prepay and then fire off multiple API requests without exposing who they are. For example, depositing 100 USDC unlocks 500 language model queries, while 10 USDC covers 10,000 Ethereum RPC calls. Each API request confirms on-chain that sufficient credits remain and that the right hasn’t been double-spent. If a user tries to reuse the same right, RLN automatically imposes a financial penalty by deducting part of the staked amount.
The system uses a “multi-call per deposit” logic for scalability. Rather than linking blockchain transaction volume to total queries, it relies on account verification and settlement intervals. For variable-cost operations, users can receive refunds for unused credits via rebate tickets, boosting flexibility and efficiency.
Infrastructure Readiness: L2 Fees Drop to $0.21
The stablecoin market now exceeds $307.6 billion in circulating supply, providing ample liquidity for this deposit-based payment model. Ethereum layer-2 scaling solutions can handle thousands of transactions per second, with average fees falling to about $0.21—a technical backdrop indicating the feasibility of Buterin’s architecture. Still, the promise of perfect privacy isn’t fully realized. Critics point out that even with cryptographic anonymity, certain metadata—such as request timing, types, or data structures—could be correlated to de-anonymize users. The RLN mechanism is currently inactive in development, and full integration will require additional software updates before real-world deployment.
API Providers Need to Embrace On-Chain Payments, Transition Likely Gradual
For the concept to gain traction, major API and AI service providers would need to adopt on-chain payment infrastructure and start accepting stablecoins. But the conventional sector already relies on deeply entrenched identity-based payment and compliance frameworks, making a shift to blockchain solutions a gradual process. Buterin, in repositioning Ethereum’s role in AI, moves away from executing applications directly on-chain. Instead, he envisions Ethereum as a neutral, programmable hub for payment and settlement. If the model gains momentum, it could further stimulate stablecoin activity and drive up transaction volumes on layer-2 networks.