Phil Zimmermann, the legendary author of Pretty Good Privacy encryption for email, has demonstrated new encryption software to secure voice over IP connections. 

Zimmermann took the stage at the Black Hat Briefings get-together for network security professionals in Las Vegas to show his session-based Zfone encryption tool.

Zfone lets two users on a Session Initiation Protocol-based VoIP connection verify each other's identity to avoid snooping. The demo ran on an Apple Mac running the open source, cross-platform Softphone and the Diffie-Hellman key agreement protocol. 

Zimmerman explained that he has received funding from VoIP pioneer Jeff Pulver and former White House terrorism advisor Richard Clarke, and some technical and business development help from PGP Corp. He plans to raise venture capital funding to speed development. 

He said that a Windows version would be ideal to make a commercial venture successful, and plans to publish a paper detailing the encryption protocol by the end of August and release the source code for Zfone for peer review.