Forcing bridged channels to be secure

Administrators can force outbound channels that are to be bridged to a calling channel to conform to secure media and signaling policies. For example, to first make a call attempt that has both secure signaling and media, but gracefully fall back to non-secure signaling and media see the following example:

• exten => 123,1,NoOp(We got a call)
  exten => 123,n,Set(CHANNEL(secure_bridge_signaling)=1)
  exten => 123,n,Set(CHANNEL(secure_bridge_media)=1)
  exten => 123,n,Dial(SIP/somebody)
  exten => 123,n,NoOp(HANGUPCAUSE=${HANGUPCAUSE})
  exten => 123,n,GotoIf($["${HANGUPCAUSE}"="58"]?encrypt_fail)
  exten => 123,n,Hangup
  
  ; notify user that retrying via insecure channel (user-provided prompt)
  exten => 123,n(encrypt_fail),Playback(secure-call-fail-retry)
  exten => 123,n,Set(CHANNEL(secure_bridge_signaling)=0)
  exten => 123,n,Set(CHANNEL(secure_bridge_media)=0)
  exten => 123,n,Dial(SIP/somebody)
  exten => 123,n,Hangup