K0: A Peer-to-Peer Electronic Payment Protocol
Abstract
A purely peer-to-peer version of electronic payments allows value to move without a custodian, without a card network in the middle, and without publishing every spend to the world. K0 is that protocol. It is defined by properties that must all hold at once: world scale, consumer-grade experience, regulatory compliance, security, and sufficient decentralization. A system that lacks any of these is not K0. Implementation follows the definition. The definition is not optional.
K0 settles in stable units of account — United States dollars as USDC, one-for-one, today; other coins later. The payer pays nothing. The merchant fee is on the order of one to ten basis points (one basis point, 0.01%, is the published design point). Privacy is cash-like by default and auditable under due process. The protocol never holds the user’s money or keys.
This paper states the protocol. Proposed machinery (wallets, chains, proofs) belongs in a separate architecture note and may or may not join K0.