RedPhone is our mobile app for end-to-end encrypted voice calls. When we talk about RedPhone, we tend to emphasize the cryptography, and how using it can help keep your communications safe. What we don’t talk about as much is the VoIP application underneath all of that, which it turns out was actually the hard part.
When we were developing RedPhone, we discovered that the cryptographic aspects of it were relatively straightforward. What we didn’t anticipate was how difficult the mechanics of delivering high quality, low latency, and highly available voice communication would be.
This describes the basic strategy we developed for the network side of low-latency and highly-available calls.