Payment Protocol

Overview

A payment protocol specifies how participants communicate payment intent and outcome. It may define invoice data, addresses, amounts, asset identifiers, expiration, signatures, callbacks, acknowledgements, errors, and settlement references. The protocol is distinct from the payment network carrying value. The same protocol can operate over different networks, and one network can support several protocols. Compatibility requires matching versions, encodings, required fields, and security assumptions.

Implementers should validate all inputs, authenticate sensitive messages, preserve idempotency, and document state transitions. Unknown fields, retries, expired requests, partial payments, and duplicate notifications need deterministic handling. A protocol can coordinate a payment without guaranteeing that the underlying transfer is valid or final, so network evidence must still be checked.

Implementations of Payment Protocol need explicit amount, currency, destination, expiry, fee, and replay rules. For Payment Protocol, wallets should show the actual transaction effects before signing, while merchants should validate execution and settlement independently of the initiating link or application. Operational handling of Payment Protocol should cover duplicate requests, expired instructions, partial payment, wrong asset or network, failed execution, and delayed confirmation. For Payment Protocol, each condition needs an idempotent business state and an auditable recovery path.

Security review for Payment Protocol should verify official domains, application identifiers, deep links, contract addresses, and update authority. For Payment Protocol, phishing-resistant presentation and independent destination checks matter whenever an external interface constructs a payment. Payment Protocol should define the parties, payment request or instruction format, supported assets and networks, authorization method, and evidence that completes the payment. For Payment Protocol, a user-interface success message is not a substitute for canonical transaction and order matching.