x402 Settlement Engine
The x402 Settlement Engine is DashPay’s core mechanism for linking offline payment proofs to on-chain finality — enabling seamless, machine-verifiable settlement of value that begins in disconnected environments and concludes with cryptographic trust.
Inspired by the long-unused HTTP 402 “Payment Required” status code, x402 introduces a standardized request/response format for payments, allowing agents, apps, devices, or humans to request a service or asset and be challenged with a verifiable payment requirement — even without an account or UI.
How x402 Works in DashPay
Request Triggered A device, user, or agent attempts to access a service, perform an action, or complete a transaction (e.g. “unlock this door”, “buy this file”, “tap to pay”).
x402 Payment Challenge Issued The recipient (merchant, API, device) returns a 402 challenge with a structured payment request — including amount, asset, chain, and optional metadata.
Proof of Payment Generated The sender responds with an ephemeral zero-knowledge proof or a signed token, confirming they meet the required balance or payment conditions — without revealing identity or address.
Local Acceptance & Logging The recipient verifies the proof offline. If valid, the action is approved and the transaction is logged as pending.
Reconnection & Reconciliation Once either party regains network access, the stored payment proof is submitted to the x402 engine, which performs zk-reconciliation, resolves conflicts, and publishes a final on-chain record.
Key Properties
Asynchronous Finality Payments do not require real-time blockchain interaction. Transactions are trustless, but not network-bound.
Chain-Agnostic Design x402 supports multiple EVM and non-EVM chains (Base, Solana, Polygon, BSC, etc.) and selects networks based on cost, latency, and availability.
No Wallet Address Exposure Transactions do not reveal public keys, wallet addresses, or metadata. All data exchanged is ephemeral and context-specific.
HTTP-Compatible Format x402 payment challenges and responses can travel through standard HTTP request flows, making them developer-friendly and bot-accessible.
Facilitator Optionality Third-party relayers can optionally monitor for payment fulfillment and return confirmation status to off-chain services — useful for merchants, APIs, or automated agents.
x402 in Action
Use cases where the x402 engine shines:
A vending machine issues a 402 challenge; the user taps and pays locally
An AI agent hits an API and receives a 402 payment requirement; it fulfills autonomously
Two users trade value over NFC; the proof settles on-chain via x402 when they reconnect
A dApp requests a pay-per-access fee; DashPay wallet handles the challenge without prompting
Why x402 Matters
Most payment systems conflate authorization, identity, and confirmation. x402 separates them — and builds a new payment layer that is:
Machine-readable
Human-optional
Offline-resilient
Privacy-preserving
Future-proof
The x402 Settlement Engine is how DashPay makes every transaction programmable, verifiable, and final — even when it starts in the dark.
Last updated