I wanted to implement a mixed mode of srtp and zrtp crypto capabilities across our network and i was facing several issues. But succeeded nonetheless. What kicked me in the balls hardest was rfc3713(taken from memory) compliance of the UAs. Whenever i wanted to set SRTP to optional on the devices sent both avp and savp lines along with the according keys in the a=crypto lines in the sdp and the zrtp-hash too. If for a reason i wanted to force ZRTP on the channel, i was supposed to set sip_secure_media to false and that would disable srtp on the b-leg and zrtp handshake would take place in p2p mode. I was using csipsimple(pjsip) though and fs was just stripping the savp from the sdp and still passing the a=crypto lines. It turned out greedy and still started talking srtp instead of zrtp. I patched it myself to strip the a=crypto too if sip_secure_media is false and it worked like a german. I wanted to know if anyone has observed how other UAs handle the srtp negotiation and if it's worth proposing my patch as an improvement on the JIRA.