Threema GmbH runs its own servers in two high-security data centers of an “ISO 27001”-certified colocation partner in the Zurich area (Switzerland).
The state-of-the-art data centers include biometric access control, full-height turnstiles, video surveillance, emergency power systems, fire protection, fail-safe air-conditioning, and a fully redundant Internet connection.
Group Calls
Apart from (some) group calls, Threema’s servers in Switzerland handle all communication. (For one-to-one calls, a direct connection will be established between the call participants if possible, which means that no server at all is involved after the call has been established.) For group calls, Threema media routers located abroad may be used to ensure a low latency and smooth communication: if group calls had to be routed through the servers in Switzerland from anywhere in the world, call participants might have a hard time to interact with each other due to high latency.
The media routers abroad are unaware of the identities / Threema IDs of a group call’s participants, and all audio/video streams are end-to-end encrypted. For technical reasons, it is necessary for the media routers to know the IP addresses of a group call’s participants while the call is ongoing. However, this information is not logged and will be deleted from the working memory right after the group call has ended.
