bitchat: Messenger that connects directly via Bluetooth LE without a phone number

This messenger features a dual-transport architecture that simultaneously utilizes a Bluetooth LE-based local mesh network and the internet-based Nostr protocol. It allows users to connect directly with nearby devices or exchange messages through Nostr relays worldwide without creating an account or registering a phone number. With low dependency on central servers, it remains functional even when communications are disrupted.

Messages are automatically routed based on the transmission path. If within Bluetooth range, the fastest and most private local path is prioritized; otherwise, it switches to the Nostr network. Nostr-based location channels use geohash coordinates to provide local chat rooms ranging from block-level to country-level coverage.

In terms of security, the Noise protocol is applied to mesh communications, and a proprietary encryption format is used for Nostr-based private messages. It is not compatible with existing Nostr standards (such as NIP-17, NIP-44, etc.) and operates only between bitchat clients. It also offers an emergency wipe feature that instantly deletes all data stored on the device.

This is a universal app with native support for iOS and macOS, written in Swift. It is suitable for users who need immediate communication means in disaster response, protest sites, or environments with difficult internet access. Distributed under a public domain license, it allows for free source verification and modification.