cairn

# Cairn **Your location, for the few you trust.** Private, end-to-end encrypted location sharing that you can host yourself. By [CappyLabs](https://cairn.cappylabs.uk). [](https://github.com/CappyTech/cairn/actions/workflows/release.yml) [](LICENSE) [](#how-it-works) [](https://flutter.dev) [Website](https://cairn.cappylabs.uk) · [Beta](https://cairn.cappylabs.uk/beta) · [Support](https://cairn.cappylabs.uk/support) · [Security](https://cairn.cappylabs.uk/security) · [Privacy](https://cairn.cappylabs.uk/privacy)
     

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Cairn lets you share your live location with the specific people you choose, and see theirs on a map. Your location — and even your display name — are end-to-end encrypted, so the server relays them but cannot read them.

Coming soon to Android and iOS. Cairn is pre-release; Android builds go to Google Play’s closed testing track. Want to try it? Sign up to test.

Why Cairn

• Private by design — location and display name are end-to-end encrypted (X25519 + ChaCha20-Poly1305). The server can’t read them.
• No account, no tracking — no email, phone, or password. Your identity is a key generated on your device. No ads, no analytics, nothing sold.
• You stay in control — pair in person, choose how precisely you share with each person, and pause or stop any time.
• Yours to run — point the app at your own server and your data never leaves it.

Features

Sharing

• 🔒 End-to-end encrypted location — only your chosen contacts can decrypt it.
• 📷 QR pairing — connect in person; only people you show your code to can pair. Not nearby? Send a one-time invite code that expires in 24 hours.
• 🎯 Per-person precision — precise, approximate (~1 km), or paused, per person; plus a global “approximate only” switch.
• ⏸️ Pause sharing for a while — for an hour, three hours, until tomorrow, or until you resume. Nobody sees you meanwhile.
• 🌙 Background sharing (optional) — keeps sharing while the app is closed, with a notification always showing, and backs off on a low battery.
• 🏷️ Status, battery, speed and direction — show a label like “Hotel”, your battery level, and (if you choose) how fast and which way you’re moving.

Map

• 🗺️ Live map — tap someone to see them with their details: freshness, distance, battery and more.
• 👥 People strip and Show everyone — jump between people, or fit everyone on screen.
• 🧭 Directions — open the route to someone, or to a shared pin, in your phone’s maps app.
• 📌 Shared pins — send a spot (“meet here”, “where I’m staying”) to chosen contacts.

History and places

• 🕓 History and trips — your trail, and the trails of people sharing with you (switchable per person), encrypted so only you can read it. Optionally snap trips to roads.
• 🏠 Places and alerts — private geofences such as Home or Work, with arrive and leave alerts.
• 🔔 Activity alerts — new connections and people going quiet, each with its own sound.

Your identity

• 🔑 24-word recovery phrase — back up and restore your identity on a new phone.
• 🗑️ Delete anytime — remove your identity and all its data from within the app.
• 🎨 Your layout — three Home layouts, and light, dark or system theme.

What the server can and can’t see

Data	Server can read?
Location	❌ No — end-to-end encrypted
Display name	❌ No — end-to-end encrypted
Location history and places	❌ No — encrypted to you
Shared pins	❌ No — encrypted to each recipient
Public keys, who’s paired with whom, timestamps	✅ Yes (pseudonymous routing metadata)

Updates go out on a fixed schedule and are padded, so their timing and size don’t reveal when you’re moving. Hiding the routing metadata (the social graph) would need a metadata-private protocol — a future goal; see docs/metadata-privacy.md and the security page.

How it works

• App: Flutter (Android; iOS pending a Mac to build).
• Backend: self-hosted PocketBase — auth, realtime, and per-record access rules. It stores only ciphertext for locations and names.
• Identity: an on-device X25519 keypair is the account; PocketBase credentials are derived from it silently.

Self-hosting

The app works against the default server, or run your own:

# on your server (Docker)
docker compose up -d          # see deploy/docker-compose.yml

The Dockerfile builds an image = PocketBase + the web build + schema migrations (pb_migrations/), so a fresh server comes up fully configured. A reverse proxy (e.g. Caddy) terminates HTTPS in front of it. Point the app at your server in Settings → Server address.

Development

flutter pub get
flutter run                                   # defaults to the production backend
flutter run --dart-define=PB_URL=http://10.0.2.2:8090   # local backend (emulator)
flutter test --exclude-tags integration       # as CI runs it
flutter test --tags integration               # needs a local PocketBase on :8090

Build a release:

flutter build appbundle --release   # signed via android/key.properties (CI provides it)

CI/CD

GitHub Actions:

• ci.yml — every pull request and non-main branch: flutter analyze and the test suite.
• release.yml, push to main → build web → push ghcr.io/cappytech/cairn-server → deploy to the edge over SSH.
• release.yml, push a tag vX.Y.Z → build a signed .aab (version from the tag), attach it as an artifact, and upload to Google Play (closed testing, alpha track) with release notes from distribution/whatsnew/.

Privacy and security

• Privacy policy
• Delete your data
• Security, and how to report a vulnerability

Licence

Cairn is free software under the GNU Affero General Public License v3.0 (AGPL-3.0). If you run a modified Cairn server for others to use, you must offer them the source of your changes.

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Cairn — your location, for the few you trust.

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