PGPfone

» see web.mit.edu/network/pgpfone as it lived, on the wayback machine

~ the obit ~

Phil Zimmermann was still under federal criminal investigation over PGP when he shipped the next thing, which was a telephone. PGPfone ran on a desktop or a notebook computer, dialed another computer's modem directly, and encrypted the voice between them. Version 1.0 was Macintosh-only and required a modem-to-modem call, with Will Price writing the Mac code; an internet-capable version followed. By July 1996 MIT was distributing beta 7 for the Macintosh and beta 2 for Windows 95 and NT, and there was an OS/2 build as well, compiled with a copy of VisualAge C++ that IBM had donated for the purpose. Microsoft donated the Visual C++ that built the Windows version, which is a detail worth sitting with given who the software was designed to defeat.

The cryptography was the straightforward part. Each call negotiated a session key with ephemeral Diffie-Hellman, so there was no key database and nothing left over afterward to subpoena. What you had instead was a conversation that nobody could store usefully, between two people who had never exchanged anything in advance.

The hard part of any key exchange is knowing you are talking to the person you dialed rather than to somebody sitting in the middle holding two separate encrypted calls. PGPfone's answer to that was your own voice. Both ends displayed the same short list of words derived from the session key, and you read yours aloud while the other person checked theirs. The manual calls this a biometric signature, and the reasoning is that an attack requires synthesizing your voice saying those particular words in real time, which in 1995 was science fiction.

Development stopped in 1997 with version 2.1. The MIT page kept advertising the betas, with a footer reading "Updated: 6/10/97", for five and a half years after that, serving a product nobody was fixing to an operating system population that was steadily moving away from it.

~ the rap sheet ~

~ us and canada only ~

The distribution page states the boundary in one sentence: "We are distributing PGPfone in the U.S. and Canada only via the World Wide Web." There were two separate forms, one American and one Canadian, and MIT ran what it described as a special purpose high efficiency web server for handing out the files. This was export control. Strong cryptography was a munition under the regulations of the day, which is the same legal theory that had put Zimmermann under investigation in the first place, and it meant that the one piece of software built specifically so that two people far apart could speak privately was only legally available if both of them were in North America.

I got online in 1998 in Turkey, three years too late and several thousand kilometers outside the download's permitted geography, on a 33.6k modem of exactly the kind this program was written for. PGP itself reached everywhere, carried by printed source code and international rebuilds. The telephone never did. Encrypted voice did not arrive at my end of the world until it came free inside something else, years later, with nobody reading words out loud to verify anything.

~ the day the page changed ~

The death certificate is unusually well documented, because the person who wrote it used a word processor that left fingerprints. On 2 February 2003 the Internet Archive captured a new version of the MIT page: the logo, then four lines of red italic text reading "MIT is no longer distributing PGPfone. Given that the software has not been maintained since 1997, we doubt it would run on most modern systems." Everything else was gone. The previous capture, on 4 December 2002, was byte-for-byte the 1997 page.

The HTML carries its own metadata. It was generated by OpenOffice.org 1.0 on Linux, created at 12:17:04 on 23 January 2003, last changed at 12:18:16, by Jeffrey Schiller, who ran MIT's network and whose email address had sat at the bottom of the old page since 1996. Seventy-two seconds in a free word processor, on a Thursday lunchtime. That is the entire funeral.

~ what came after ~

Zimmermann came back to the problem in 2006 with Zfone, built on a protocol called ZRTP that does the same ephemeral key exchange over modern voice-over-IP and still has you compare a short authentication string out loud. ZRTP went to the IETF and ended up in other people's software, which is a better afterlife than PGPfone got.

The other thing that happened in 2003 was Skype, which launched seven months after MIT pulled the page and gave millions of people encrypted-sounding calls they never had to configure. MIT still serves the PGPfone logo at its old address, a 2 KB GIF of the wordmark with "pretty good privacy" set underneath it, which is now the only part of the product you can still download from there.

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