For signaling, nothing magic with OStel - we are using standard SIP over TLS. The TLS certifcates are based on the standard Root CA trust model. We are looking

For signaling, nothing magic with OStel - we are using standard SIP over TLS. The TLS certifcates are based on the standard Root CA trust model. We are looking into pinning as possible feature for the Android CSipSimple app. We are already supporting features like pinning and trust on first use (TOFU-POP) in Gibberbot, so we understand the importance here of those advanced features. Ultimately, our focus with OStel (and the larger Open Secure Telephony Network) is to build best-practice based secure voice systems built on free software, that work like the Internet does. This also means apps like Jitsi, Groundwire, SFLPhone and other compliant clients can work just as well with our system as the primary Android app we focus on.