<-- HTML Generated by MacWeb on 12Oct94 (at 23:09:54) --> PGP: The Privacy Wars

PGP: The Privacy Wars

by Deborah Russell

Cryptography used to be an arcane subject of interest only to the most secret military and intelligence agencies and to a handful of academics. Things have changed. Suddenly it seems that everyone is talking about encrypting their files and electronic mail. Internet fans are touting public key cryptography as a vital lane on the information highway. Former anti-war and nuclear freeze activists are now protesting against U.S. government cryptographic policy. Hackers who only yesterday were breaking into government and university computers are now demanding the right to secure their own communications. The new slogan is "Encyption for the masses!"

What's going on here?

The center of much of the excitement over encryption these days is a program called PGP, for Pretty Good Privacy. Written by Phil Zimmermann and first released in 1991, PGP actually provides really good privacy. It's a powerful piece of software that uses state-of-the-art cryptography to protect files and electronic mail. Freely available and widely distributed on the Internet , PGP has become very popular both in the U.S. and abroad. Its use extends well beyond the traditional realm of computer security products. Zimmermann tells stories about Burmese freedom fighters who keep their communications hidden from government eyes by using PGP on PCs in jungle camps, about Eastern Europeans who believe that PGP will protect them in case their fragile republics collapse, and about a myriad of more pedestrian uses of PGP to protect business secrets and love letters.

Our upcoming book, PGP: Pretty Good Privacy , by Simson Garfinkel, is both a highly readable technical user's guide and a fascinating behind-the-scenes look at the development and the politics of PGP and cryptography in general. The book is loaded with useful examples and comes with a tear-out command reference card.

PGP has gained widespread use despite -- or maybe because of -- an array of legal problems that have rallied public support for the program and its author by partisans of privacy and free speech. Its author has faced attacks on PGP from two powerful foes: the U.S. government on the one hand and RSA Data Security/Public Key Partners on the other, as we'll describe below.

What Does PGP Do?

PGP encrypts data files and electronic mail so their contents are completely private. PGP uses public key cryptography to encrypt keys, though it relies on much faster private key cryptography (the IDEA block cipher algorithm) to encrypt actual messages.

To exchange encrypted mail with a friend -- let's call him Joe -- using PGP's public key cryptography, you and Joe must each have created two keys: a public key and a private key. You keep your private key a secret, but you let Joe (and anybody else you exchange mail with) know what your public key is. When you send Joe a message, you encrypt your message with his public key. When Joe receives the message, he decrypts it with his secret key. Only Joe will be able to decrypt the message (you won't even be able to!).

With PGP, keys are kept in PGP's "key certificates," which are stored in files known as "key rings."

PGP does more than encrypt. Its ability to produce digital signatures lets you "sign" and authenticate messages. A digital signature is a unique mathematical function derived from the message you send. You sign a message by applying your secret key to it before you send it. By checking the digital signature for a message, the recipient can make sure that the message hasn't been altered during transmission. The digital signature can also prove that you, and you alone, sent the message. No one (including you) can deny it.

PGP has a very easy-to-use command line interface, works on virtually every platform, and gives you many options that allow you to tune the program to your own security needs.

PGP and Patents

PGP's use of public key cryptography invades the turf carved out by RSA Data Security and Public Key Partners who claim that the inner workings of PGP too closely resemble those of the patented RSA algorithm.

The RSA algorithm (named for its developers Ronald Rivest, Adi Shamir, and Leonard Adleman) was announced in a 1977 MIT technical report. That same year, MIT filed for a patent on RSA which was granted in 1983 (U.S. patent #4,405,829). The RSA patent and several other public key patents were exclusively licensed to Public Key Partners, a spinoff from RSA Data Security (founded by the RSA developers).

Because Zimmermann's PGP software uses the RSA public key algorithm (although, according to Zimmermann, he did not use any copyrighted RSA code), Public Key Partners' president Jim Bidzos has threatened Zimmermann with legal action for violating patent law. Acrimony between the two has raged for several years.

Finally this spring, PGP came out of the legal shadows. A new, freely available (for noncommercial purposes) toolkit, RSAREF, was released by RSA Data Security. Zimmermann ripped apart the PGP encryption engine and replaced it with the RSAREF toolkit. Although it's likely that Bidzos never intended the toolkit to give PGP a break in this way, it nevertheless cleared the way for PGP's legitimacy.

In May of 1994, MIT, Bidzos, and Zimmermann agreed to a new deal for PGP. MIT would become the official distribution site for a new version of PGP, 2.6. Zimmermann would make changes so that PGP 2.6 could not decrypt messages encrypted with the old "illegitimate" versions of PGP. And RSA/PKP would not pursue its legal battles with Zimmermann.

PGP and Export Restrictions

In the eyes of the U.S. government, cryptography -- even the weakest kind -- is considered to be munitions. The most dangerous arms dealer and the most mild-mannered cryptographer are equally suspicious characters. The government closely regulates the sale and export of crypto. Government spokespeople say that export regulations are intended to restrict the use of products that could ultimately make an enemy nation's communications more difficult for U.S. intelligence agencies to decipher.

In most cases, if you export PGP or any other cryptographic product (even one built into your operating system or application package), you will be violating State Department, Defense Department, and Commerce Department regulations. The only way to export crypto legally outside the U.S. is with a license granted by the State Department Office of Munitions Control through the International Traffic in Arms Regulations (ITARs).

Despite these regulations, PGP got out of the U.S. early and often. Zimmermann says he never sent the software abroad himself, but through the magic of the Internet a few copies abroad became hundreds, and soon many thousands.

Zimmermann has been investigated by the State Department and other government agencies as a result of the export of PGP. In an odd blend of patent and export issues, he's also the target of a criminal investigation by the U.S. Customs Agency for sending allegedly stolen software outside the U.S. As a consequence, he could face a jail term.

PGP and the Clipper Chip

Not coincidentally, PGP has reared its populist head at the same time that the U.S. government's Clipper Chip proposals have come under public scrutiny.

What is Clipper? It's an encryption chip based on a classified cryptographics algorithm called Skipjack that is said to be more powerful than any available to ordinary citizens in the past. The U.S. government wants private industry to build Clipper into telephones, FAX machines, and other communication products so encryption would be part of our communications. Clipper is expected to be relatively cheap, virtually unbreakable, and (unlike most strong cryptography) available to everyone, not just spies and sleuths. So, what's the catch?

The catch -- and one that has civil libertarians and those who call themselves Cypherpunks raging -- is that built into Clipper is a "back door" concept called key escrow. You and I can shield our communications from most of the world because we share a secret key. But we're not completely secure. At the time our secret keys were assigned, an extra copy was entrusted to the care of the government. If somewhere down the road the government suspects that we are planning a crime or an uprising, an agency like the FBI would (with a wiretap order) be able to use the escrowed key to listen in on our communications.

The Clipper debate rages. On one side, the government warns that, without Clipper, nuclear terrorists, drug dealers, and pedophiles will roam freely in cyberspace. On the other, respected academics, the Electronic Frontier Foundation, and grass roots Cypherpunks demand electronic privacy as a basic right and warn of Big Brother.

Zimmermann's attack on Clipper, through PGP, is more subtle than most being mounted. To a large extent, the very existence of PGP -- virtually unbreakable, free, and unencumbered by the key escrow threat -- represents the most serious threat to Clipper, simply because it offers such an attractive alternative for those who crave privacy but fear governmental interference.

Zimmermann writes: If privacy is outlawed, only outlaws will have privacy. Intelligence agencies have access to good cryptographic technology. So do the big arms and drug traffickers. So do defense contractors, oil companies, and other corporate giants. But ordinary people and grassroots political organizations mostly have not had access to affordable "military grade" public key cryptographic technology. Until now.

The world of modern cryptography is one that extends beyond the narrow confines of technology to touch upon fundamental issues of privacy, government control, and personal freedom. Just as PGP is more than simply a piece of software, PGP: Pretty Good Privacy is more than simply a Nutshell Handbook for the use of the program. We think you'll find its technical exposition informative and its background stories thought-provoking. Wherever you stand on the issues raised by PGP, Clipper, and privacy initiatives, you'll find something of value in this wide-ranging book.

Deborah Russell is the editor of the O'Reilly & Associates' computer security series and the coauthor of Computer Security Basics and Love Your Job .

Simson Garfinkel is a journalist and the author of Practical UNIX Security , NeXTStep Programming (Springer-Verlag), and The UNIX-Haters Handbook (IDG).

This article will appear in the upcoming fall 94 issue of ora.com .