Answer by andolini7110

andolini7110 — Wed, 04 Feb 2015 02:28:44 -0500

I had the same problem and after lot of searching on the web, I didn't find any solution to it. I switched over to VoIPInvite SIP services and i am pretty happy with their services.

Answer by landroni

landroni — Mon, 18 Aug 2014 14:30:41 -0400

I think I managed to figure out this one. In the end the issue doesn't seem to be on Linphone's side at all. It turns out that some SIP providers do NOT support transporting traffic through TLS (Iptel or Antisip), while others do support that: Linphone SIP service or Ostel.

To avoid the error above and to place a secure SIP call via TLS and using ZRTP encryption I had to do the following:

upgrade to Linphone 3.7.0: "possible to configure multiple proxy accounts with different transports (UDP, TCP, TLS)"
add a SIP account in Linphone using Linphone SIP service or Ostel SIP providers
for each account, in the SIP Account Configuration dialogue set Transport to TLS (instead of UDP)
in Options > Prefs > Network Settings set Media encryption type to ZRTP

Now you can check that all works as expected by calling the Ostel Echo testing service sip:9196@ostel.co and verifying that you see the message Secured by ZRTP - [auth token: ab34]. I suspect that the NSA should have a harder time intercepting that..

Answers to: Error when configuring Linphone to use SIP (TLS) and ZRTP encryption

Answer by andolini7110

Answer by landroni