I recently attended a talk about GNU Telephony. I was informed that Twinkle supports ZRTP for encrypted SIP calls.
I went into Edit > User Profile > Security and made sure that ZRTP was enables and that all boxes were checked. I asked a friend to do the same and then we called each other. There is no immediate indication that I can see that the call is secure.
How can I tell if ZRTP is enabled in a Twinkle SIP call?