Dude, you skipped the next sentence...alvinma wrote: ↑ "When a device receives a push notification about a pending incoming call, it launches the softphone application. The softphone creates a special SIP user agent which communicates directly with SIPIS. Next, the softphone notifies SIPIS about its “readiness” and SIPIS then proceeds by initiating its own SIP call with the device. This new call is constructed using most of the information from the real incoming call, so from the iPhone’s point of view it just seems as if the call came directly from the calling party (while it is, in fact, just iPhone – SIPIS “tunnel”). Once this new call is established, SIPIS relays all relevant signaling information between these two separate calls."
https://doc.acrobits.net/sipis/overview ... light=push
Meaning it's only the SIP signalling that is proxied NOT the actual call audio.Once this new call is established, SIPIS relays all relevant signaling information between these two separate calls. Note that while SIP signaling goes always through the SIPIS, RTP media streams don’t.
This is not to say that they couldn't log all call audio if they wanted, but so can everyone else on the internet.
VOIP calls aren't encrypted (they can be but you'd have to use ZRTP or something similar and both parties would need to support it)