Book Image

Mastering FreeSWITCH

By : Russell Treleaven, Seven Du, Darren Schreiber, Ken Rice, Mike Jerris, Kalyani Kulkarni, Florent Krieg, Charles Bujold
4 (1)
Book Image

Mastering FreeSWITCH

4 (1)
By: Russell Treleaven, Seven Du, Darren Schreiber, Ken Rice, Mike Jerris, Kalyani Kulkarni, Florent Krieg, Charles Bujold

Overview of this book

FreeSWITCH is one of the best tools around if you’re looking for a modern method of managing communication protocols through a range of different media. From real-time browser communication with the WebRTC API to implementing VoIP (voice over internet protocol), with FreeSWITCH you’re in full control of your projects. This book shows you how to unlock its full potential – more than just a tutorial, it’s packed with plenty of tips and tricks to make it work for you. Written by members of the team who actually helped build FreeSWITCH, it will guide you through some of the newest features of version 1.6 including video transcoding and conferencing. Find out how FreeSWITCH interacts with other tools and APIs, learn how to tackle common (and not so common) challenges ranging from high availability to IVR development and programming advanced PBXs. Great communication functionality begins with FreeSWITCH – find out how and get your project up and running today.
Table of Contents (21 chapters)
Mastering FreeSWITCH
Credits
About the Authors
About the Reviewers
Contributors
www.PacktPub.com
Preface
7
WebRTC and Mod_Verto
Index

Encrypting (S)RTP via SDES (key exchange in SDP)


SRTP in its oldest, simplest and most deployed implementation encrypts the (UDP) audio stream using a key that was exchanged via SIP(S), in the SDP body of the SIP packet.

This method, called SDES (SDP Security Descriptions), can be considered secure under two conditions:

  • Encrypted SIPS (for example, TLS) was used for exchanging keys in signaling

  • All the SIP(S) proxies between caller and callee are trusted

Because SIP(S) packets must be interpreted by proxies, the organizations that own or manage each single proxy between caller and callee know the key and can decrypt the audio. Also, someone can succeed in inserting him or herself into the proxy chain, and acting as a man-in-the-middle (mitm), pretending to be one such legitimate proxy, and then decrypt and/or tamper with the audio.

Many wrongly identify "SRTP" with "SRTP via SDES". SRTP is actually RTP encrypted via keys, and there are many different methods to exchange those keys.

Anyway, anyone...