Ethereum's zkAPI Breaks AI Payment Trails with Zero-Knowledge Proofs

The Ethereum Foundation has introduced a new system called zkAPI, which aims to break the trail of identity left behind by AI payments. The system allows users to deposit funds into an Ethereum vault and later pay for AI requests without revealing their identity. This is achieved through a zero-knowledge proof, which verifies that the user has sufficient funds without revealing the source of the funds.

zkAPI separates payment from identity, making it difficult for the AI provider to connect the user's identity with their payment history. The system also creates a fresh, short-lived key for each payment, which lives only in the user's device memory. This key is used to authorize the payment, and when it expires, the provider records the amount consumed in a signed usage receipt.

The zkAPI system is still experimental, and the Ethereum Foundation notes that there is no invisibility cloak. The provider still receives prompts and responses, and network information can betray the user's identity. The Foundation also warns that shared prompt contents can act as fingerprints for users who can read the prompts.

Despite these limitations, zkAPI has the potential to be used not just for AI payments, but also for other services such as blockchain RPC queries, image and video jobs, and machine-to-machine services.