MeshChat 📡

Off-grid, end-to-end encrypted chat over a Bluetooth + local-network mesh.

MeshChat lets nearby devices exchange messages with no internet, no server and no account — messages hop peer-to-peer across the mesh until they reach their recipient, encrypted end-to-end so relay nodes can never read them.

Built with .NET MAUI (Android / iOS / Windows) on a transport-agnostic mesh core.

How it works

┌─────────────┐     BLE / TCP      ┌─────────────┐     BLE / TCP      ┌─────────────┐
│   Alice     │ ──────────────────▶│   Relay      │ ──────────────────▶│   Bob       │
│  (sender)   │   encrypted packet │  (can't read │   encrypted packet │ (recipient) │
└─────────────┘                    │   payload)   │                    └─────────────┘
                                   └─────────────┘

• End-to-end encryption — ephemeral ECDH key agreement + AES-GCM authenticated encryption per message; relay nodes forward opaque packets and can never decrypt payloads.
• Mesh routing — packets carry a TTL and hop across intermediate peers (store-and-forward), so two devices out of direct range can still communicate.
• Multi-transport — Bluetooth LE for off-grid proximity plus TCP over the local network, with mDNS peer discovery; the transport orchestrator picks whatever path is available.
• No infrastructure — no server, no account, no phone number. Peers are identified by the hash of their public key.

Solution layout

Project	What it does
MeshChat.Core	Transport-agnostic domain: MeshRouter (routing, TTL, dedup), CryptoService (ECDH + AES-GCM), PeerStore / MessageStore (SQLite), TransportOrchestrator
MeshChat.BLE	Bluetooth LE transport — Android and iOS platform implementations
MeshChat.Network	Local-network transport — TCP framing + mDNS peer discovery
MeshChat.Relay	Headless relay node (console) for extending the mesh
MeshChat.MAUI	Cross-platform UI — chat and peer management
MeshChat.Tests	xUnit suite: crypto round-trips, routing, store-and-forward, end-to-end scenarios

Tests

dotnet test MeshChat.Tests

An additional Python end-to-end harness (MeshChat.Tests/e2e_test.py) exercises full multi-peer scenarios — encryption interop, multi-hop relay delivery and TTL expiry — against the protocol implementation. run-tests.sh / run-tests.bat run everything.

The repo also ships a Claude Code skill that automates running and extending the E2E suite.

Status

Working prototype. BLE transport is implemented for Android and iOS; the local-network transport and relay are functional on desktop. Contributions and issue reports are welcome.

License

MIT