How To Make Your Phone Untappable

In 1991, Philip Zimmermann developed a humble-sounding electronic encryption technology known as Pretty Good Privacy. In fact, it was very good--so good that not even the federal government has been able to crack it, a fact that has made Zimmermann a folk hero to privacy advocates and a headache to law enforcement.

Now Zimmermann, a fellow at Stanford Law School's Center for Internet and Society, has found himself back in the fiery debate between federal investigators and those who oppose their snooping--this time thanks to ZRTP, a technology for encrypting Internet telephone calls. ZRTP throws a wrench in the Bush administration's controversial warrant-free wiretapping program and its proposed legal immunity for the telecommunications companies. So far, not even teams of supercomputers and cyberspies at the National Security Agency have cracked ZRTP. That means anyone who uses Zimmermann's Zfone software, a ZRTP-enabled voice over Internet Protocol (VoIP) program available for free on his Web site, can skirt the feds' wiretapping altogether.