Warning

This is an experimental software based on bitchat-android Expect bugs and instability.

SignalOut for Android

A secure, decentralized, peer-to-peer messaging app that works over Bluetooth mesh networks. No internet required for mesh chats, no servers, no phone numbers - just pure encrypted communication. SignalOut also supports geohash channels, which use an internet connection to connect you with others in your geographic area.

This project is a fork of the original project bitchat with a WhatsApp-style UI redesign and new features. It maintains protocol compatibility where applicable.

Install SignalOut

You can download the alpha version of SignalOut for Android from the GitHub Releases page

Direct Download:

Instructions:

1. Download the APK: On your Android device, navigate to the link above and download the latest .apk file. Open it.
2. Allow Unknown Sources: On some devices, before you can install the APK, you may need to enable "Install from unknown sources" in your device's settings. This is typically found under Settings > Security or Settings > Apps & notifications > Special app access.
3. Install: Open the downloaded .apk file to begin the installation.

License

This project is released into the public domain. See the LICENSE file for details.

Features

• ✅ WhatsApp UI Redesign: Modern WhatsApp-like interface including dark/light themes, typography, custom message bubbles, doodle patterns, and redesigned chat headers/inputs.
• ✅ Voice & Video Calling over WIFI Direct: Real-time voice and video calling powered by WebRTC.
• ✅ File & Media Attachments: Support for sending documents, images, and audio directly in chats.
• ✅ Cross-Platform Compatible: Full protocol compatibility with iOS SignalOut
• ✅ Decentralized Mesh Network: Automatic peer discovery and multi-hop message relay over Bluetooth LE
• ✅ End-to-End Encryption: X25519 key exchange + AES-256-GCM for private messages
• ✅ Channel-Based Chats: Topic-based group messaging with optional password protection
• ✅ Store & Forward: Messages cached for offline peers and delivered when they reconnect
• ✅ Privacy First: No accounts, no phone numbers, no persistent identifiers
• ✅ IRC-Style Commands: Familiar /join, /msg, /who style interface
• ✅ Message Retention: Optional channel-wide message saving controlled by channel owners
• ✅ Emergency Wipe: Triple-tap logo to instantly clear all data
• ✅ Modern Android UI: Jetpack Compose with Material Design 3
• ✅ Dark/Light Themes: Terminal-inspired aesthetic matching iOS version
• ✅ Battery Optimization: Adaptive scanning and power management

Android Setup

Prerequisites

• Android Studio: Arctic Fox (2020.3.1) or newer
• Android SDK: API level 26 (Android 8.0) or higher
• Kotlin: 1.8.0 or newer
• Gradle: 7.0 or newer

Build Instructions

1. Clone the repository:

   git clone https://github.com/techflyers/signalout.git
   cd signalout

2. Open in Android Studio:

   # Open Android Studio and select "Open an Existing Project"
   # Navigate to the signalout directory

3. Build the project:

   ./gradlew build

4. Install on device:

   ./gradlew installDebug

Development Build

For development builds with debugging enabled:

./gradlew assembleDebug
adb install -r app/build/outputs/apk/debug/app-debug.apk

Release Build

For production releases:

./gradlew assembleRelease

Android-Specific Requirements

Permissions

The app requires the following permissions (automatically requested):

• Bluetooth: Core BLE functionality
• Location: Required for BLE scanning on Android
• Network: Expand your mesh through public internet relays
• Notifications: Message alerts and background updates

Hardware Requirements

• Bluetooth LE (BLE): Required for mesh networking
• Android 8.0+: API level 26 minimum
• RAM: 2GB recommended for optimal performance

Usage

Basic Commands

• /j #channel - Join or create a channel
• /m @name message - Send a private message
• /w - List online users
• /channels - Show all discovered channels
• /block @name - Block a peer from messaging you
• /block - List all blocked peers
• /unblock @name - Unblock a peer
• /clear - Clear chat messages
• /pass [password] - Set/change channel password (owner only)
• /transfer @name - Transfer channel ownership
• /save - Toggle message retention for channel (owner only)

Getting Started

1. Install the app on your Android device (requires Android 8.0+)
2. Grant permissions for Bluetooth and location when prompted
3. Launch signalout - it will auto-start mesh networking
4. Set your nickname or use the auto-generated one
5. Connect automatically to nearby iOS and Android signalout users
6. Join a channel with /j #general or start chatting in public
7. Messages relay through the mesh network to reach distant peers

Android UI Features

• Jetpack Compose UI: Modern Material Design 3 interface
• Dark/Light Themes: Terminal-inspired aesthetic matching iOS
• Haptic Feedback: Vibrations for interactions and notifications
• Adaptive Layout: Optimized for various Android screen sizes
• Message Status: Real-time delivery and read receipts
• RSSI Indicators: Signal strength colors for each peer

Channel Features

• Password Protection: Channel owners can set passwords with /pass
• Message Retention: Owners can enable mandatory message saving with /save
• @ Mentions: Use @nickname to mention users (with autocomplete)
• Ownership Transfer: Pass control to trusted users with /transfer

Security & Privacy

Encryption

• Private Messages: X25519 key exchange + AES-256-GCM encryption
• Channel Messages: Argon2id password derivation + AES-256-GCM
• Digital Signatures: Ed25519 for message authenticity
• Forward Secrecy: New key pairs generated each session

Privacy Features

• No Registration: No accounts, emails, or phone numbers required
• Ephemeral by Default: Messages exist only in device memory
• Cover Traffic: Random delays and dummy messages prevent traffic analysis
• Emergency Wipe: Triple-tap logo to instantly clear all data
• Bundled Tor Support: Built-in Tor network integration for enhanced privacy when internet connectivity is available

Performance & Efficiency

Message Compression

• LZ4 Compression: Automatic compression for messages >100 bytes
• 30-70% bandwidth savings on typical text messages
• Smart compression: Skips already-compressed data

Battery Optimization

• Adaptive Power Modes: Automatically adjusts based on battery level
  • Performance mode: Full features when charging or >60% battery
  • Balanced mode: Default operation (30-60% battery)
  • Power saver: Reduced scanning when <30% battery
  • Ultra-low power: Emergency mode when <10% battery
• Background efficiency: Automatic power saving when app backgrounded
• Configurable scanning: Duty cycle adapts to battery state

Network Efficiency

• Optimized Bloom filters: Faster duplicate detection with less memory
• Message aggregation: Batches small messages to reduce transmissions
• Adaptive connection limits: Adjusts peer connections based on power mode

Technical Architecture

Binary Protocol

signalout uses an efficient binary protocol optimized for Bluetooth LE:

• Compact packet format with 1-byte type field
• TTL-based message routing (max 7 hops)
• Automatic fragmentation for large messages
• Message deduplication via unique IDs

Mesh Networking

• Each device acts as both client and peripheral
• Automatic peer discovery and connection management
• Store-and-forward for offline message delivery
• Adaptive duty cycling for battery optimization

Android-Specific Optimizations

• Coroutine Architecture: Asynchronous operations for mesh networking
• Kotlin Coroutines: Thread-safe concurrent mesh operations
• EncryptedSharedPreferences: Secure storage for user settings
• Lifecycle-Aware: Proper handling of Android app lifecycle
• Battery Optimization: Foreground service and adaptive scanning

Android Technical Architecture

Core Components

1. SignaloutApplication.kt: Application-level initialization and dependency injection
2. MainActivity.kt: Main activity handling permissions and UI hosting
3. ChatViewModel.kt: MVVM pattern managing app state and business logic
4. BluetoothMeshService.kt: Core BLE mesh networking (central + peripheral roles)
5. EncryptionService.kt: Cryptographic operations using BouncyCastle
6. BinaryProtocol.kt: Binary packet encoding/decoding matching iOS format
7. ChatScreen.kt: Jetpack Compose UI with Material Design 3

Dependencies

• Jetpack Compose: Modern declarative UI
• BouncyCastle: Cryptographic operations (X25519, Ed25519, AES-GCM)
• Nordic BLE Library: Reliable Bluetooth LE operations
• Kotlin Coroutines: Asynchronous programming
• LZ4: Message compression (when enabled)
• EncryptedSharedPreferences: Secure local storage
• WebRTC: Voice and video calling

Publishing to Google Play

Preparation

1. Update version information:

   // In app/build.gradle.kts
   defaultConfig {
       versionCode = 2  // Increment for each release
       versionName = "1.1.0"  // User-visible version
   }

2. Create a signed release build:

   ./gradlew assembleRelease

3. Generate app bundle (recommended for Play Store):

   ./gradlew bundleRelease

Future Implementations

1. LoRA: Planned support for long-range transmission of emergency messages using LoRA technology.
2. AI Routing: Using AI to route messages based on priority, urgency of message, availability of peers and network conditions through the mesh network.

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