The Slack bridge supports end-to-end encryption (E2EE) rooms, using pantalaimon. This means the bridge will encrypt messages when sending to E2EE rooms, and will decrypt them to be sent to Slack. New direct messages (DMs) and private channels will also be encrypted by default when bridged.
The end-to-end encryption is established between Matrix clients and the bridge. Messages going to and from Slack will be encrypted by HTTPS but won’t use E2EE. Bridge encryption secures conversation contents on all Matrix homeservers and clients it is sent to. Also, this may be advantageous to users of Enterprise Key Management.
You must first setup the pantalaimon daemon. This must be accessible by the bridge but SHOULD NOT be accessible to users of your homeserver. Docker users should take care to ensure that the Pantalaimon container can be reached by the bridge container.
Then you should add the following to the configuration file:
encryption: enabled: true pantalaimon_url: "http://127.0.0.1:8009"
pantalaimon_url is the URL where your bridge can reach the daemon.
Afterwards, any new DMs or private rooms will be encrypted. Also, any existing rooms connected to the bridge that have encryption enabled will also be encrypted going forward.
If you choose to disable this feature later, the bridge will not create new DM rooms, so you will need to delete the existing encrypted rooms from the DB and start over.