A new feature that encrypts data when syncing it with untrusted devices has been in early testing the past few months. With the release of v1.15.0-rc.1 we invite everyone interested to test it. Do not use it yet for important data, it is still meant for testing.
The feature is still hidden behind a feature flag:
To show controls for untrusted devices in the web UI, you need to add
untrusted to the
featureFlags options - either through Actions > Advanced in the web UI or by adding the
<featureFlag>untrusted</featureFlag> element within
<options> in the config.xml.
User documentation: Untrusted (Encrypted) Devices — Syncthing v1 documentation
Design and implementation documentation: Untrusted Device Encryption — Syncthing v1 documentation
Please ask questions about the feature here on the forum and report bugs you encounter to the issue tracker - if in doubt just post on the forum.