BitChat vs iGap

BitChat is a decentralized messaging app that uses Bluetooth mesh for nearby communication and Nostr relays for internet messaging. Bluetooth messages can pass between nearby devices across as many as seven hops without internet access. When Bluetooth is unavailable, the app can use Nostr; if neither route is available, messages can wait in a queue. Geographic chat rooms use geohash coordinates.

The app requires no account, phone number, or central server. Live mesh sessions use Noise XX for mutual authentication and forward secrecy, while private Nostr messages use an app-specific encrypted format that works only with BitChat clients. However, mesh announcements expose static keys and nicknames in cleartext, and a persistent per-device identifier can allow nearby listeners to follow a device over time and place. A triple-tap emergency wipe clears app data, including identity keys and queued messages. Android adds Wi-Fi Aware on supported devices and built-in Tor. BitChat is available for iOS, Android, and macOS, and is free.

iGap has no write-up on Specifiction yet; its figures are above.