How is the communication protected in Threema Broadcast?
In Threema Broadcast, all messages are always transmitted in encrypted form. On top of that, incoming messages are not stored (unless the option “Save chat history” is enabled in centrally managed group chats).
Messages sent via the Threema Broadcast web interface are protected using TLS while in transit between your browser and the Threema Broadcast server. The Threema Broadcast server then encrypts the messages again using Threema’s regular end-to-end encryption based on NaCl. The private key of a Broadcast ID is stored in symmetrically encrypted form for each customer to prevent unauthorized access by third parties.
Messages that administrators send with feeds, distribution lists, and in group chats are stored on the Threema Broadcast server and can be accessed by the administrators of the relevant Broadcast ID in the Threema Broadcast web interface.Incoming messages
Messages that Threema users send to a feed or distribution list are not stored and cannot be accessed by administrators of the Broadcast ID. These messages are immediately deleted from the server.
Only centrally managed groups offer the option to save the entire chat history (including incoming messages).Duration of storage
Files are permanently deleted after 30 days, and text messages after 180 days in Threema Broadcast.