"The peace movement in the mid-'80s was in an adversarial relationship with the White House, and I felt grassroots political organizations needed a way to protect their data," Zimmermann said, sitting barefoot in jeans and a Hawaiian shirt at his San Francisco Bay area home.

What started as a human rights project,Zimmermann also wanted to give people in other countries protection from oppressive governments,became a technology with lasting impact worldwide. Ten years after its release as freeware, PGP remains a popular means of achieving privacy on the Internet.

"He's the unlikeliest hero I've ever met," said John Perry Barlow, co-founder and vice chairman of the Electronic Frontier Foundation, a San Francisco-based civil liberties organization. "He doesn't fit the profile. He's mild, unassuming, quiet, and he did something at the time that was immensely heroic and had far-reaching effects."

Despite a federal government that was cracking down on regulations against the export of strong cryptography and threatening him with indictment, Zimmermann persevered, driven by a belief "that people have a right to privacy and freedom of expression," Barlow said.

PGP became an international standard for cryptography used by businesses and "millions of grateful individuals," he said.

Before PGP, cryptography was primarily the government's domain, said Zimmermann colleague Patrick Ball, deputy director of science and human rights programs at the American Association for the Advancement of Science (AAAS), based in Washington.

"Privacy was not available to anybody but the government. Phil fundamentally changed that equation by building PGP and putting it out there," Ball said. "Phil made strong cryptography available to pretty much anyone who cared to learn how to use it."

Zimmermann is "a classic computer guy, a nerd," Barlow said. But "he's a very thoughtful nerd. He's a nerd with a social conscience."

PGP was a way to preserve some of the privacy and civil liberties people enjoyed before the advent of the digital age, said Zimmermann.

"Technology is making surveillance easier. It's making it easier to intercept e-mail and phone calls and all matter of electronic communication," he said. "One countermeasure is to apply cryptography. It doesn't solve the whole problem, but it solves the parts of the problem I knew how to solve."

Zimmermann, 47, grew up in Florida, an only child in a blue-collar family. His father drove a cement truck and his mother was a homemaker. A self-proclaimed science-fiction addict, Zimmermann got a job at a bookstore in the 10th grade and was paid partly in used books, mostly sci-fi.

Intent on becoming an astronomer, Zimmermann started as a physics major at Florida Atlantic University in Boca Raton. Then he discovered computers. Mesmerized by something that was "kind of cool and mysterious," he switched majors to computer science.

Zimmermann was working as a software engineer and was married with two kids when he and his wife joined the peace movement. Being a peace activist was nearly a full-time job for Zimmermann, who taught classes in military policy, trained lobbyists and participated in the Nuclear Weapons Freeze Campaign. While protesting nuclear weapons testing at the Nevada Test Site, he was arrested twice, along with public figures such as Sagan, Sheen and Daniel Ellsberg, of Pentagon Papers fame.

"Every time I see Martin Sheen on 'West Wing,' I remember being in the slammer with him," Zimmermann said with a laugh. "We were only in it for a day. They let us out because there were so many of us."

But the experience influenced his creation of PGP. "This gave me my perspective that it is sometimes better to take direct action to change unjust laws, which helped guide me in developing PGP," he said.

When starting his research on cryptography, Zimmermann found few papers published on the subject. The reason: the National Security Agency had a near monopoly on the technology, he said. He developed components for PGP through the late 1980s, and in 1991 released the software as freeware, propelling its adoption.

Two years later, however, Zimmermann found himself the target of a government investigation for allegedly violating federal encryption export laws. In building their case, prosecutors subpoenaed documents and witnesses, including Zimmermann's friends. He was faced with the prospect of a sentence of up to 51 months in federal prison.

But then, in early 1996, the government dropped its case. Zimmermann speculates that the combination of an election year and a statute of limitations that was slated to run out in six months contributed to the demise of the case.

That same year, Zimmermann and Jonathan Seybold founded PGP Inc. Seybold describes Zimmermann as a highly sophisticated thinker who can put technology to practical use.

"He realized that with the advent of this digital world, we've opened up an enormous ability to communicate but we're also putting that personal communication at risk in the process," Seybold said. "So his objective was to use technology to get back part of what technology was taking away."

Yet Zimmermann also struggles with the fact that encryption technology has a dark side, Seybold added.

"If you're protecting privacy for the good people, you're also protecting privacy for the bad people," he said. "That's something you worry about morally, but it's a price you have to pay in the end because if you don't, then nobody has privacy."

Friends and business associates describe Zimmermann as down-to-earth with a wry sense of humor. Still, Seybold said Zimmermann sometimes can be a bit of an absent-minded professor. For instance, when Zimmermann was recounting his creation of PGP, he suddenly remembered that he had forgotten to eat breakfast,at 11 a.m.

Mark McArdle, who started working with Zimmermann as an engineer at PGP in 1996, recalled that Zimmermann had achieved the status of an Internet folk hero after the government scrapped its investigation.

"[That was] because of PGP and his commitment to providing a tool that allows people to have some privacy on this wonderful new medium," McArdle said.

While working with Zimmermann to bring PGP to the corporate world in the face of bureaucratic encryption export restrictions, McArdle said he came to understand Zimmermann's fervent belief in the need for strong encryption and why he made personal sacrifices to make PGP become a reality. The Clinton administration eventually relaxed the encryption export laws in 2000.

Zimmermann is technologically savvy, but he's also politically aware and understands the human implications of technology, said AAAS' Ball. Ball used PGP in his human rights work before meeting with the standard's creator at a conference in 1998. He said PGP was critical to protecting data while he was working on a book about statistical patterns in human rights violations in Guatemala.

Ball invited Zimmermann to a presentation of his report in Guatemala, and the two traveled through the countryside, meeting people who used PGP.

"I think the thing he's most proud of is the way in which this technology has helped protect people all over the world, particularly people who are dissidents in areas where there are oppressive regimes," Seybold said.

Commercial applications of PGP haven't had a major market impact, but they set the stage for the future of encryption-based technology in the enterprise, said Frank Bernhard, managing principal at Omni Consulting Group, a Davis, Calif.-based technology economics firm. "[PGP] enforced the need for privacy throughout not just your own e-mail but your whole enterprise," Bernhard said.

After Network Associates acquired PGP in December 1997, Zimmermann worked at the company as a senior fellow for three years. He left Network Associates earlier this year, citing differences in opinion about the future of PGP. He now works as a consultant on cryptography-related projects. Network Associates, meanwhile, last month announced plans to dissolve its PGP Security division.

Besides privacy, Zimmermann has a passion for film. Seybold calls Zimmermann "a walking encyclopedia of film" and said he often makes references to various movies.

As for the future, Zimmermann said he sees a tougher road ahead in terms of protecting personal privacy. For example, cryptography can't protect privacy when it comes to video surveillance, he said.

"We need to solve this through different means,perhaps some legislation that prohibits what that technology is used for, or fight it with our social expectations," he said. "We have to have people outraged by this."

Computer algorithms that can read body language present more Orwellian-like implications, Zimmermann said.

"I know how to fix e-mail. I can secure e-mail. I know how to encrypt data," he said. "I don't know how to solve the other problems, but I'll work on the ones I know how to solve."