Secure RTP with Asterisk

Normal asterisk servers use RTP for deliver audio over the internet. Any one can capture this RTP streams by using Packet Sniffer tools, and can listen to  the call content. So VoIP calls are not secure for confidential communications until using a secure VoIP system.

Therefore we can use advance protocol called SRTP (Secure Real-time Transport Protocol) which provide encryption for RTP stream. So no one can listen to the VoIP conversations while using SRTP. If someone try to capture the SRTP stream, it will play only a noise (even it was a empty conversation).

But it will not complete the secure VoIP system. You MUST secure the signalling (SIP) because SRTP keys are exchanged in plaintext with SDES( To do that we have to use Asterisk TLS (Transport Layer Security). It provides encryption for call signaling.

Asterisk 1.8 has native support for SRTP. So you can easily try this with a Asterisk 1.8.x server. The normal SIP phones are not support for this system. You need to find SRTP supported and TLS supported IP/soft phones for setup this. Use blink soft-phone for this ( I followed following article to setup secure VoIP system.

For SRTP :
For TLS :, ( You can find ast_tls_cert script from here :

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What will happen to the Future of VOIP?

Almost every person who can afford a phone has one. Some have more then one. so now it is the telecommunication era. Internet is also everywhere now and in the near future Traditional phone systems will be replaced by VoIP (Voice Over Internet Protocol). Because it is very low cost and easy maintenance. And also there are lot of advance features we can have using VOIP technology.

In the USA, many cell phone service providers are seeing the potential of incorporating VOIP in there services.  They will be able to charge users for this extra service which means more money.

Mobile is growing tremendously with new phones that are capable of handling VOIP such as Google Android, iPhone, and Windows Mobile.

Video over IP is also already in use now and follows the same concept as VoIP but in this case enables the transmission of video signals.

A new beginning will begin soon for VOIP.

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