Scrambler-phone technology - will it be available for aircraft mobiles?

by Guy Kewney | posted on 31 July 2005

It may be cheaper to use VoIP through your PC than to talk on a phone - but it sure as heck isn't more secure - as Pretty Good Privacy pioneer Phil Zimmerman reminds us. He's fixing this with a new bit of software - and he sees this as giving rivals a "leg up" on Skype in the Internet phone business.

Guy Kewney

According to VoIP guru Jeff Pulver, the Zimmerman invention is a SIP (session initiation protocol) client phone - he's seen it demonstrated on his own Free World Dialup network.

From the Black Hat security conference, comes a ZDNet report: "The prototype, called "zfone," should be available online at the end of August, along with accompanying documentation," the Joris Evers report quotes  Zimmermann.

Apparently the VoIP client is based on the open-source Shtoom VoIP phone client, with added cryptography.

According to Ryan Naraine at this isn't Zimmerman's first encrypted IP phone. The report points to the PGPFone software package from 15 years ago, before people had broadband.

The prototype seen by Pulver is not available for PC laptops, however, so the prospect of seeing secure voice from aircraft is pretty remote, unless you have a Mac computer. But says that the technology will make SIP at least as secure as Skype - reminding users that Skype is actually encrypted, but with an unpublished algorithm.

Zimmerman is reluctant to take Skype security on trust, it seems.

His prototype, according to Charlie Demerjian at the Inquirer, is written in the Python language, so should be portable. "Based on a lot of work done for Zimmerman's PGP phone many years ago, this new one is written in Python, mainly because it is built off of Shtoom, another Python program," writes Demerjian. "What zfone does is lower the entry barrier for VOIP calling while eliminating one big class of attack, the man in the middle.

  • Black Hat report from ZDNet news
  • Analysis from
  • Personal Zimmerman Portrait from TechWorld
  • Inquirer offers  tech details
  • Pulver's take in his blog.

  • Terribly Good Telephone privacy - You can discuss this article on our discussion board.