TransportChat

Source available on GitHub: https://github.com/AlsatianConsulting/TransportChat-Android TransportChat is a peer-to-peer encrypted messaging app built for teams and individuals who need secure communication without relying on the internet, cloud servers, or third-party infrastructure. All messages stay on your local network — or your private overlay network (Tailscale, ZeroTier, WireGuard) — and never leave it. KEY FEATURES • End-to-End Encryption — Every message is encrypted using the Signal Protocol. No server ever sees your plaintext. • No Internet Required — Works entirely over your local Wi-Fi or private VPN overlay. Zero cloud dependency. • Group Chats — Create named groups with pairwise fan-out encryption. Every member gets their own encrypted copy. • File Sharing — Send files of any type with an offer/accept flow. Multi-file sends are automatically zipped. • Voice & Video Calls — One-to-one encrypted WebRTC calls over the local network. No STUN, no TURN, no cloud relay. • Identity Verification — Verify contacts with a 5-word safety phrase derived from their public key. Detects key changes automatically. • VPN & Overlay Network Support — Automatically discovers peers on Tailscale, ZeroTier, and WireGuard networks in addition to local Wi-Fi. • App Lock — Protect the app with a PIN, password, or pattern. Optional biometric (fingerprint/face) unlock backed by the Android Keystore. • Zero Configuration — Peers are discovered automatically via UDP broadcast and overlay network scanning. No accounts, no pairing codes, no QR setup required. • Encrypted Database — All data is stored with SQLCipher (AES-256) on device. Nothing persists in plaintext. DESIGNED FOR • Field teams and first responders operating in network-isolated environments • Facility networks (warehouses, hospitals, campuses) that restrict internet access • Security-conscious individuals who want provably private communication • IT professionals and researchers using private overlay networks PRIVACY BY DESIGN TransportChat collects zero data. There are no accounts, no phone numbers, no email addresses. Your identity is a locally-generated cryptographic key pair. Nothing is transmitted outside your local network. OPEN ARCHITECTURE The transport layer supports LAN broadcast, multicast, and unicast heartbeat to known peers — all configurable without touching settings. Overlay network peers are scanned and discovered automatically when a VPN interface is detected. Minimum Android 10 (API 29) required.