Tap-proof and as privacy-friendly as it gets
Just like Threema messages, Threema calls are end-to-end encrypted and thus tap-proof. In contrast to conventional messengers, Threema doesn’t use a phone number as unique identifier. Instead, a randomly generated Threema ID serves this purpose, which means that no personally identifiable information is contained in metadata. Furthermore, it’s possible to make calls without disclosing one’s phone number to the called party.
The call connection is established using Threema messages in the background. Therefore, voice calls are just as trustworthy as chats, and the same verification levels apply. If possible, a direct connection between caller and callee is established (peer to peer), which improves the call quality considerably. Because a constant bit rate is used for audio encoding, no conclusions about the content can be drawn from the size of the transmitted data packets.
High stability thanks to public beta test
Several thousand enthusiastic Threema users have participated in the beta program. Due to the high demand as well as limitations by Apple, the quota of beta testers for the iOS app was reached within a few hours. The bug reports we received have enabled us to identify and eliminate minor bugs. Thanks to the extensive testing, Threema calls have gained high stability and reliability. We would like to thank everyone who helped testing Threema calls!