How security works
The short version: only the person holding the watch can add it to an account, and only that account can see its data. A serial number alone gets nobody anything.
1. Syncing reads, never writes
The unstrap program lists your watch's files and reads the ones that are new or changed. It never writes to or deletes from the watch. It skips folders that hold Wi-Fi credentials, maps, firmware and logs.
2. Proving it's your watch
Serial numbers are printed on the watch and visible to any computer it's plugged into, so we never trust them. Instead, every sync proves it holds the watch: the server picks a few files it already has from your watch and sends a fresh random challenge, and the program must answer with a fingerprint (HMAC) of those exact files. Only the real watch, or your own account, has those bytes.
Someone uploading made-up files under your serial number can't answer, so their uploads go into a separate, empty store that never touches yours.
3. Adding a watch to your account
You click Add a watch, signed in. For 10 minutes, the next sync from the same network as your browser (same home internet connection) is added to your account. Someone elsewhere can't use your window, and you can't take a watch that belongs to someone else: a watch is added once, and only its owner can release it.
4. Signing in
No passwords. We email a link that works once, for 20 minutes. Opened in the browser that asked for it, it signs you in straight away; opened anywhere else, it asks you to confirm first. That stops mail scanners from using it, and stops anyone from signing you into their account by sending you a link.
5. Storage
- Files and database in the EU (Cloudflare D1 and R2, EU jurisdiction).
- Everything travels over HTTPS.
- We never store IP addresses: network matching uses a keyed fingerprint of the network (salted HMAC).
- Sign-in links and session cookies are stored only as fingerprints (SHA-256).
6. Keeping and deleting
- Data from a watch nobody added is deleted 30 days after its last sync.
- Deleting a watch or your account removes everything about it immediately; the files are purged from storage overnight.