Jitsi (Bulgarian for Wires) is a multi-protocol and multi-platform voice and video instant messenger client. It is mostly implemented in Java, and is Free/Open Source software. Its multi-protocol features are similar to that of Kopete, the native IM client for the K Desktop Environment. In a previous incarnation, Jitsi was known as SIP Communicator.

Where other VoIP services and clients send data in the clear, Jitsi sets itself apart by making use of ZRTP to set up secure communication with SRTP, Secure Real-time Transport Protocol. Other clients use plain Real-time Transport Protocol, RTP. By itself, ZRTP is not the security protocol, but the mechanism used to generate and exchange keys between both ends of the VoIP session.

It (ZRTP) was developed by Phil Zimmermann, and is used in his own Zfone software. It is likely that your favorite Linux distribution does not have a jitsi package in its repository, but there are .deb and rpm packages that you can download and install. The following screenshots show the process involved.

If you are using a distribution that uses the Debian packaging framework, you can initiate the installation process by downloading a 32- or 64-bit package from here.Note: Jitsi is still beta software and the packages are nightly builds).
 Jitsi Deb Package Download

Once you click OK in the previous window, you will see this one. Click Install Package.
Jitsi Deb Package Install

If you are using an RPM-based distribution, you may download a compatible package here (also a nightly build). The installation process is the same as that on a Debian-based distribution.

Jitsi is mostly implemented in Java, so you will need Java installed first. If Java is not installed, you will get this friendly error message.
Jitsi Java Dependency

Once installed, there should be an entry for Jitsi in the menu’s Internet software category. The main interface of the application with its dial pad are shown below. It is just like any other IM or VoIP client.
Jitsi Dial Pad

This screenshot shows the protocols or services that you may use via Jitsi. If you have an account in one or more, you can set them all up, so they will all be available from the main Jitsi interface.
Jitsi IM Services

This screenshot just shows some of the configurable options in Jitsi.
Jitsi Options

Jitsi uses ZRTP and SRTP to secure your communication by default, but if you are a guru, you can mess with ZRTP settings from this window.
Jitsi ZTRP Options

Jitsi even lets you set up multi-party calls. If you have used Jitsi, or will use it after reading this article, let us know if it worked for you.
Jitsi Conference