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A Tour Through Zfone

This review of Zfone is intended for readers who would like to take a look at Zfone but are too busy to test it at the moment. The visual aids used in this article may also help readers to grasp some of the concepts (such as key continuity) behind Zfone. The complete specification of ZRTP, the key exchange protocol used by Zfone, can be found in this Internet draft. Zfone is available for Windows XP, Mac OS X and Linux, and can be downloaded for free from its official homepage.


Installing Zfone should take only a couple of minutes. You may encounter a number of warning messages presented by Windows XP along the way, but they can be ignored. Despite its name, Zfone is not a stand-alone softphone, but rather, a “bump in the cord” (as described in its homepage) that encrypts RTP packets generated by a softphone. There is not much you need to do to get Zfone up and running, assuming that your softphone works properly prior to the Zfone installation and that Zfone is launched before the softphone.

After installation, Zfone would automatically launch itself and sit in the system tray. Zfone also installs a ZRTP driver that can be verified by opening the property menu of any LAN card installed in the system. Zfone also automatically checks with a designated server to see if there is any new update available. Since I used an isolated network as my test bed, Zfone complained “Can’t connect to libzrtp server” at the bottom of the GUI.


Figure 1: Zfone control panel

The Zfone GUI looks very clean (Figure 1). In fact, what’s conspicuous about the GUI is its lack of any configuration menu. Basically there are only three things you can do when the system is idle: check for new version, read help and exit.

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