bitchat

BitChat is a decentralized peer-to-peer messaging app with a dual transport architecture. It combines local Bluetooth mesh networking for offline communication with the Nostr protocol for internet-based global messaging. The project states there are no accounts, phone numbers, or central servers, and it is released into the public domain. For offline use, BitChat supports Bluetooth Low Energy peer discovery, direct peer-to-peer messaging, multi-hop relay up to seven hops, Noise Protocol encryption for mesh sessions, compact binary packet formatting, and adaptive battery duty cycling. For internet messaging, it uses Nostr relays with location-based channels defined by geohash coordinates at block, neighborhood, city, province, and region precision. Private internet messages use BitChat-specific private envelopes carried in kind-1059 events with XChaCha20-Poly1305 encryption; these are not NIP-17, NIP-44, or NIP-59 compatible and only interoperate with BitChat clients. Direct messages use intelligent routing: Bluetooth first when available, Nostr fallback when not, and queuing when neither transport is available. The app includes IRC-style commands such as /slap, /msg, and /who, native iOS and macOS support, emergency wipe by triple-tap, LZ4 message compression, and local build instructions for Xcode and Just. The repository also provides guidance for verifying builds against per-release hash manifests.