SAMVAD — Secure Ad-hoc Mesh Voice for Assured Defense

A voice-first, offline-capable communicator: peer-to-peer, no mandatory server, with an automatic transport fallback — internet first, degrading to a Bluetooth Low Energy mesh when there's no internet available. Every packet is end-to-end encrypted regardless of which transport is active.

Primary use case: disaster relief and off-grid/humanitarian response. Secondary, dual-use case: squad-level comms where issuing certified tactical radios to every operator isn't practical.

Status

Two tiers are implemented and verified working end-to-end on real hardware:

• Internet tier — live duplex voice call over WebRTC (Opus), with a Noise XX handshake run in parallel over the signaling channel so both parties can visually confirm a fingerprint before trusting the call.
• BLE mesh tier — push-to-talk voice notes over a direct Bluetooth LE connection. Every device runs both GATT roles at once (central + a custom native peripheral/GATT-server plugin), so two phones can find and connect to each other with no prior pairing. Payloads are Noise-encrypted before they touch the radio.

A third tier (RF/LoRa mesh, for when neither internet nor BLE range is available) is scoped as a documented roadmap item, not built here — see "Known limitations" below.

Repo layout

server/   Node.js WebSocket signaling server (internet tier only —
          relays WebRTC SDP/ICE and opaque Noise handshake bytes between
          exactly two peers; never sees anything else)
web/      The app itself: Vite + React + TypeScript, wrapped with
          Capacitor for the Android build. This is the whole client —
          web/android is the native shell around the same code.

Running it

# signaling server
cd server && npm install && npm start

# web app (also usable directly in a browser for the internet tier)
cd web && npm install && npm run dev

For the Android build:

cd web
npm run build
npx cap sync android
cd android && ./gradlew assembleDebug   # or assembleRelease, with a keystore.properties in place

BLE mesh only works from the native Android build — browsers only expose BLE Central mode (scanning), never peripheral/advertising, on any platform.

Codec

The internet tier uses Opus (WebRTC's default). The BLE tier's codec module (web/src/lib/codec.ts) is currently a placeholder built on the browser's WebCodecs AudioEncoder pinned to a low Opus bitrate — Codec2 (700–1200 bps, the actual target for a bandwidth-starved BLE/RF link) needs libcodec2 cross-compiled to WASM, which isn't wired up yet. Swapping it in only touches that one file.

Known limitations

• The RF/LoRa tier is not implemented — internet and BLE only.
• BLE is single-hop (two directly-connected devices), not yet a multi-hop flooding relay across a larger mesh.
• The Noise identity keypair is stored in browser localStorage, keyed per-origin — clearing app data or reinstalling generates a new identity.
• On at least one tested chipset, running both BLE roles (central + peripheral) concurrently on the same device silently hangs the GATT connection on the central side — the connection succeeds at the OS level, but the JS-visible connect() promise never resolves. A per-device role selector (Both / Peripheral only / Central only) in the BLE panel works around this reliably; confirmed working end-to-end (discovery, GATT connect, Noise handshake) on real hardware with roles isolated.