Protecting SIP signalling

SIP signaling is important to encrypt. It contains both authentication information your phone utilizes to make and receive calls and it includes the Caller ID Name and Number of the caller and callee, by default in plain text. This is easy to sniff and to spoof. Encryption makes that harder. In addition, if you are using SRTP (Secure RTP), the SIP signaling contains the cryptography key used to keep your audio secure. Someone who observed this key in plain-text would easily be able to defeat the media encryption utilized.

Choosing between encryption options

There are a variety of encryption options available for FreeSWITCH. You can encrypt the signaling (that is, the SIP messages), the media (that is, the audio in the RTP stream), or both. Transport Layer Security (TLS) V1 encrypts everything over the TCP connection; this has the downside that jitter or delays due to TCP can occur. UDP is generally preferred for RTP and using TLSV1 has some additional traffic overhead...