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Bitconnect

Offline Bluetooth mesh chat + worldwide end-to-end encrypted DMs.

No accounts. No phone numbers. Messages hop phone-to-phone over BLE when offline, or travel the world as pure E2E ciphertext over public Nostr relays.
Product name Bitconnect
Version 1.3.0+ (mesh protocol v2)
Platforms Android (primary), iOS scaffolded
Workspace path C:\bitconnect

What you can do

Local mesh (Bluetooth)

  • Multi-hop BLE gossip on multiple channels (#local, #general, #alerts, custom)
  • High TX power + low-latency scan for better practical range
  • Phones relay for each other (effective range grows with density)
  • Signed public posts (Ed25519); optional group E2E with a shared channel key
  • Images over mesh — compressed, multi-chunk transfer, one bubble, tap to open full screen
  • Delivery ACKs and read receipts (✓ / ✓✓)
  • Store-and-forward ferry for text when peers reappear
  • Power modes: Performance / Balanced / Saver (LPN-style)

Worldwide E2E (Internet)

  • Private 1:1 DMs India ↔ USA (or any distance) when both have internet
  • X25519 ECDH + ChaCha20-Poly1305 encryption on-device
  • Relays cannot read message text
  • Share identity via copy ID or paste

Not private

  • Default mesh channels (#local, etc.) are readable by anyone on the mesh
  • Use Create E2E group in Settings for encrypted local rooms

Install (Android)

APK

dist/bitconnect-release.apk

Most modern phones: arm64. Prefer a split ABI build for smaller size (see below).

adb install -r dist\bitconnect-release.apk

Or copy the APK to the phone and open it (allow install from unknown sources).

Requirements: Android 8+ (API 26), Bluetooth for mesh, Internet for Worldwide DMs.

Smaller APKs (recommended)

A single “fat” APK bundles multiple CPU architectures (~70MB+). Split builds are much smaller:

$env:JAVA_HOME = "C:\Program Files\Eclipse Adoptium\jdk-17.0.19.10-hotspot"
$env:ANDROID_HOME = "$env:LOCALAPPDATA\Android\Sdk"
$env:PATH = "$env:JAVA_HOME\bin;C:\Users\hafil\flutter\bin;$env:PATH"

cd apps/mobile
flutter pub get
flutter build apk --release --split-per-abi

Outputs:

File Use
app-arm64-v8a-release.apk Most modern phones (use this)
app-armeabi-v7a-release.apk Older 32-bit phones
app-x86_64-release.apk Emulators

Copy the one you need:

copy build\app\outputs\flutter-apk\app-arm64-v8a-release.apk ..\..\dist\bitconnect-release.apk

App map (UI)

Bottom navigation:

Tab Purpose
Local Mesh channel chat, start/stop mesh, photos, receipts
Worldwide E2E DMs, connect relays, contacts

In-app:

Entry Purpose
Tune / Settings Power mode, public channels, create/join encrypted groups
Channel chips Switch #local / custom channels
Image Attach photo (mesh: compressed multi-chunk; Worldwide: larger)
Tap image Full-screen pinch-zoom viewer

Media quality notes

  • Mesh images are compressed for BLE multi-chunk delivery: max 720px, JPEG ~56 KB target, down-scaled with high-quality average interpolation to preserve clarity within the BLE size limit.
  • Worldwide images keep a larger 1024px / ~140 KB envelope for internet E2E.
  • Rendering uses FilterQuality.high in both the chat bubble and the full-screen viewer for the sharpest on-screen result.
  • Binary file packet (TLV: name / size / mime / content) — not JSON base64 chat spam.
  • Split into binary BLE fragments, reassembled into one bubble.
  • Tap the thumbnail → full-screen open.
  • Prefer Worldwide if you need much larger photos (mesh is capped by BLE fragment size).

First-run flows

Local mesh demo (two phones)

  1. Install Bitconnect on both devices.
  2. Set nicknames.
  3. Local → start mesh (tether icon) → allow Bluetooth / nearby devices.
  4. Chat on #local. Keep the app open for best results.
  5. Optional: ⋮ menu → Simulator mode for single-device multi-hop tests.

Worldwide E2E (any distance)

  1. Both phones online.
  2. Worldwide → Copy my ID.
  3. Friend pastes your ID → Save & chat.
  4. Connect relays → send locked messages.

Encrypted local group

  1. Settings → channel name → Create E2E group.
  2. Share the key out-of-band (secure chat / in person).
  3. Friend: Settings → paste key → Join encrypted channel.

Repo layout

apps/mobile/                 Flutter app (Material 3 dark theme)
  assets/branding/           App logo
  lib/src/
    theme/                   Brand theme
    screens/                 Local, Worldwide, Settings, image viewer
    widgets/                 Bubbles, chips, composer
packages/
  mesh_protocol/             Packets, gossip, crypto, ferry, media chunks (pure Dart)
  mesh_transport/            FakeTransport + multi-node sim fabric
  mesh_ble/                  BLE central + Android dual-role bridge
  mesh_internet/             Nostr client + Internet E2E service
docs/
  PROTOCOL.md                Mesh wire format
  E2E_INTERNET.md            Internet E2E threat model
  DEMO.md                    Multi-phone demo checklist
dist/
  bitconnect-release.apk     Installable build (when present)

Architecture

┌──────────────────────────────────────────────────┐
│  Flutter UI  (Local | Worldwide)                 │
│  Theme · Settings · Image viewer                 │
├────────────────────┬─────────────────────────────┤
│  MeshController    │  Identity (Ed25519+X25519)  │
├────────────────────┼─────────────────────────────┤
│  MeshNode          │  InternetE2eService          │
│  gossip · ACK/read │  Nostr relays (ciphertext)  │
│  ferry · rate limit│  X25519 sealed boxes        │
│  group crypto      │                             │
│  media chunks      │                             │
├────────────────────┼─────────────────────────────┤
│  BLE / Fake        │  WebSocket relays           │
└────────────────────┴─────────────────────────────┘
  • mesh_protocol has no Flutter dependency — unit-tested.
  • Bitconnect ID (shareable) = X25519 public key hex (64 chars).

Internal IDs (kept on purpose)

Item Value Why
Android applicationId app.bitconnect.bitconnect Stable installs/upgrades
Flutter package name bitconnect Import / path stability
Secure storage keys bitconnect_* Existing identities still load
Protocol tags bitconnect-e2e-v1, magic NT Wire compatibility

Develop

Prerequisites

  • Flutter 3.22+ (e.g. C:\Users\hafil\flutter)
  • JDK 17 for Android builds (JDK 26 is too new for current Gradle)
  • Android SDK (%LOCALAPPDATA%\Android\Sdk)
$env:PATH = "C:\Users\hafil\flutter\bin;$env:PATH"
$env:JAVA_HOME = "C:\Program Files\Eclipse Adoptium\jdk-17.0.19.10-hotspot"
flutter doctor

Run

cd apps/mobile
flutter pub get
flutter run

Tests

cd packages/mesh_protocol
dart pub get
dart test

Covers multi-hop gossip, E2E seal/open, rate limit, ferry, group crypto.

Security summary

Surface Behavior
Public mesh channels Not confidential — anyone on the mesh can read
Encrypted mesh groups Shared-key E2E (share key out-of-band)
Worldwide DMs Pure E2E; relays see ciphertext only
Nicknames Not unique — trust fingerprint / Bitconnect ID
Keys flutter_secure_storage on device

Do not put secrets on open #local. Use Worldwide E2E or an encrypted group.

Details: docs/E2E_INTERNET.md · docs/PROTOCOL.md

Known limits

Topic Reality
BLE range ~tens of meters per hop; multi-hop needs intermediate phones
Mesh images Small thumbnails by design; large photos use Worldwide
Background mesh Best with app open; iOS dual-role is best-effort
Nostr delivery Depends on public relays (no guarantee like WhatsApp)
App size Prefer --split-per-abi; fat multi-ABI APK is larger
Signing Release APK uses debug signing (sideload OK, not Play Store)

Demo checklist

See docs/DEMO.md for two-phone mesh, multi-hop, and Worldwide E2E acceptance steps.

License

MIT — see LICENSE.

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Bluetooth Mesh communication, E2E encryption for enhanced privacy and security

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