Securing Asterisk with SRTP and SIPS

Hello Asterisk Community,
while planning a greater setup of Asterisk I’m struggling with the possibilities for secure VoIP inside a LAN in cominbation with Hardphones like snom sells them.

As I see it, there are the following two problems:

  1. Who calls whom
    A sniffer in the LAN could get information, which people Mr. X calls, because of the SIP protocol. Thats why SIPS is needed.

  2. Whats the content of the call
    The voice audio information needs to be protected, thats why SRTP is needed.

I found the following link, but I’m not sure how far the integration of SRTP is progressed:

Are there other sources or projects which progressed further with this topic?

Perhaps it is possible to develop own code, but I’m not sure where to start.

Every help and information is appreciated