Jack Dorsey Releases BitChat: Encrypted Messaging via Bluetooth LE Mesh

A secure, decentralized, peer-to-peer messaging app that works over Bluetooth mesh networks. No internet required, no servers, no phone numbers - just pure encrypted communication.

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

• 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
• Room-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 room-wide message saving controlled by room owners
• Universal App: Native support for iOS and macOS
• Cover Traffic: Timing obfuscation and dummy messages for enhanced privacy
• Emergency Wipe: Triple-tap to instantly clear all data
• Performance Optimizations: LZ4 message compression, adaptive battery modes, and optimized networking

1. Install XcodeGen if you haven't already:

2. Generate the Xcode project:

   cd bitchat xcodegen generate

3. Open the generated project:

1. Open the project in Xcode:

   cd bitchat open Package.swift

2. Select your target device and run

1. Open Xcode and create a new iOS/macOS App
2. Copy all Swift files from the bitchat directory into your project
3. Update Info.plist with Bluetooth permissions
4. Set deployment target to iOS 16.0 / macOS 13.0

• /j #room - Join or create a room
• /m @user message - Send a private message
• /w - List online users
• /rooms - Show all discovered rooms
• /clear - Clear chat messages
• /pass [password] - Set/change room password (owner only)
• /transfer @user - Transfer room ownership
• /save - Toggle message retention for room (owner only)

1. Launch bitchat on your device
2. Set your nickname (or use the auto-generated one)
3. You'll automatically connect to nearby peers
4. Join a room with /j #general or start chatting in public
5. Messages relay through the mesh network to reach distant peers

• Password Protection: Room 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

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

• 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
• Local-First: Works completely offline, no servers involved

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

• 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

• 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

bitchat 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

• 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

For detailed protocol documentation, see the Technical Whitepaper.

1. Set your development team in project settings
2. Configure code signing
3. Archive and distribute through App Store or TestFlight

The protocol is designed to be platform-agnostic. An Android client can be built using:

• Bluetooth LE APIs
• Same packet structure and encryption
• Compatible service/characteristic UUIDs