Offline-first settlement infrastructure

AirPay

A hybrid blockchain payment platform that keeps value moving when mobile networks disappear, then synchronizes promises back to Solana when connectivity returns.

View on GitHubExplore the protocol

2 modes

online settlement and offline promises

Solana

final audit and settlement layer

Local-first

device-to-device exchange path

Online like instant payments. Offline like a programmable digital check.
English page

Why it exists

Payments should not collapse just because the network is overloaded.

AirPay combines wallet custody, local transport, cryptographic signatures, backend observability, and smart-contract settlement so merchants and users can keep operating through rural dead zones, large events, emergency outages, and unstable mobile networks.

Instant when reachable

If either side can reach the chain path, the experience converges toward direct settlement and familiar instant-payment behavior.

Deferred when isolated

When both sides are offline, the sender issues a signed promise with policy limits, local risk scoring, and later reconciliation.

Public by design

The source code, mobile wallet, FastAPI service, shared protocol, and Anchor program are published as one inspectable monorepo.

Modes

One payment system, two operating conditions.

The protocol chooses the safest available route at transaction time. Connectivity unlocks direct submission; disconnection falls back to bounded promises with a tamper-evident journal.

Online route

Offline promise

1

Wallet signs a Solana transfer or OffAir promise.

2

Policy and capacity limits gate the transaction before handoff.

3

NFC bootstraps the peer session and BLE carries the encrypted payload.

4

Receipts, journals, and promise state sync when a device returns online.

System map

A hybrid stack instead of a central payment switch.

The backend provides operational services, but it is not the source of truth for settlement. Final integrity lives in signatures, journals, and on-chain records.

Mobile

Android wallet and local transport

Mnemonic custody, Solana intent signing, NFC bootstrap, BLE transfer, local journals, readiness checks, and trust prompts.

React Native / Expo

Protocol

Shared rules and cryptographic payloads

Canonical hashes, policy gates, risk snapshots, wallet identity material, and offline transfer envelopes.

TypeScript package

Backend

Operational sync and recovery

Device registration, policy fetch, budget provisioning, pending transaction sync, logs, risk, and reconciliation metadata.

FastAPI

Chain

Final settlement and audit

Anchor program accounts for wallet profiles, promise claims, reserves, metadata, settlement batches, and penalties.

Solana / Anchor

Risk model

Offline payments are promises, so the system treats limits as a core product surface.

AirPay does not pretend an isolated promise is already final money. It constrains exposure before exchange and makes later reconciliation verifiable.

Policy-bound limits

Maximum amount, transfer count, allowance capacity, and device state are checked before an offline promise leaves the wallet.

Cryptographic accountability

Wallet, device, and post-quantum signature bundles bind each promise to canonical payloads and peer receipts.

Tamper-evident journals

Local histories use chained hashes so reconciliation can detect gaps, replacement, replay, and inconsistent settlement.

Programmable reputation

The beta track expands risk scoring, anti-fraud rules, and smart-contract driven limit reductions for repeated default behavior.

Build phases

From MVP protocol to resilient payment network.

The current repository targets MVP validation while leaving room for stronger reputation, mesh networking, SDKs, and marketplace integrations.

MVP

Wallet, signatures, limits, deferred sync

  • Basic wallet
  • Online SOL path
  • Offline promises
  • Policy and capacity checks

Beta

Reputation and automated risk

  • Advanced contracts
  • Fraud monitoring
  • Mesh experiments
  • Operational analytics

Scale

Public integrations

  • Marketplace APIs
  • SDK
  • Distributed sync
  • Multi-chain research

Open the repository and inspect the protocol.

The public project includes the website, mobile wallet, backend, shared protocol package, Solana contracts, demo docs, and Kubernetes manifests.

Open GitHubRead demo flow