permissionlesstech / bitchat

## bitchat
A decentralized peer-to-peer messaging app with dual transport architecture: local Bluetooth mesh networks for offline communication and internet-based Nostr protocol for global reach. No accounts, no phone numbers, no central servers. It's the side-groupchat.
bitchat.free
📲 App Store
📲 Play Store
### Getting a copy you can trust
Install from the App Store, or build from source you have verified. A compiled build from anywhere else cannot be verified — see Verifying bitchat for how to check source against the per-release hash manifest, and for what to do if that is the only build you can get.
This matters more than it usually would: this repository has been the target of takedown demands, and when a repository or releases page disappears, mirrors appear that nobody can check.
## License
This project is released into the public domain. See the LICENSE file for details.
## Features
- **Dual Transport Architecture**: Bluetooth mesh for offline + Nostr protocol for internet-based messaging
- **Location-Based Channels**: Geographic chat rooms using geohash coordinates over global Nostr relays
- **Intelligent Message Routing**: Automatically chooses best transport (Bluetooth → Nostr fallback)
- **Decentralized Mesh Network**: Automatic peer discovery and multi-hop message relay over Bluetooth LE
- **Privacy First**: No accounts, no phone numbers, no servers. Note that the mesh does use a persistent per-device identifier derived from your identity key — see the whitepaper on identity and metadata for what a nearby radio can observe
- **Private Message End-to-End Encryption**: Noise Protocol for mesh, BitChat private envelopes for Nostr fallback
- **IRC-Style Commands**: Familiar `/slap`, `/msg`, `/who` style interface
- **Universal App**: Native support for iOS and macOS
- **Emergency Wipe**: Triple-tap to instantly clear all data
- **Performance Optimizations**: LZ4 message compression, adaptive battery modes, and optimized networking
## Technical Architecture
BitChat uses a **hybrid messaging architecture** with two complementary transport layers:
### Bluetooth Mesh Network (Offline)
- **Local Communication**: Direct peer-to-peer within Bluetooth range
- **Multi-hop Relay**: Messages route through nearby devices (max 7 hops)
- **No Internet Required**: Works completely offline in disaster scenarios
- **Noise Protocol Encryption**: End-to-end encryption, with forward secrecy for live sessions (store-and-forward mail is sealed without it — see the whitepaper)
- **Binary Protocol**: Compact packet format optimized for Bluetooth LE constraints
- **Automatic Discovery**: Peer discovery and connection management
- **Adaptive Power**: Battery-optimized duty cycling
### Nostr Protocol (Internet)
- **Global Reach**: Connect with users worldwide via internet relays
- **Location Channels**: Geographic chat rooms using geohash coordinates
- **440+ Relay Network**: Distributed across the globe for reliability
- **BitChat Private Envelopes**: App-specifi