Philip Zimmermann is an American cryptographer best known as the creator of Pretty Good Privacy, or PGP, the email encryption software he released for free in 1991, and which became the most widely used email encryption tool in the world.
His release of PGP triggered a three-year US federal criminal investigation, and his work is widely cited within cypherpunk and crypto history as a foundational influence on the privacy-focused ideas that later shaped Bitcoin.
Who Is Philip Zimmermann?
Philip Zimmermann earned a bachelor’s degree in computer science from Florida Atlantic University in 1978. In the 1980s, he settled in Boulder, Colorado, working a day job as a software engineer while moonlighting as a policy analyst for the Nuclear Weapons Freeze Campaign. He became an active participant in the anti-nuclear protest movement of the mid-1980s and was arrested at a protest at the Nevada Test Site alongside astronomer Carl Sagan and actors Martin Sheen, Kris Kristoferson, and Robert Blake.
His political organizing work convinced him that activists needed better tools to protect their communications from government surveillance, an idea he had wanted to pursue since the 1980s but lacked the time to build until years later.
Philip Zimmermann’s Career and Contributions
On June 5, 1991, Zimmermann published PGP for free on Peacenet, an online network of political activists, followed shortly after by a post on USENET. PGP applied public key encryption, a technique previously used mainly by corporations and government agencies, to ordinary email for the first time at scale. He named the software after a fictional grocery store featured on the radio show A Prairie Home Companion. Zimmermann even missed five mortgage payments while developing the software in the first half of 1991. However, the release drew the attention of federal investigators.
In February 1993, two federal agents contacted Zimmermann, and a grand jury in California was assembled to determine whether he had violated US weapons-export law, since strong encryption was legally classified as munitions at the time. A successful prosecution could have resulted in up to five years in prison and a fine of up to $1 million. The investigation lasted three years before the government dropped the case in early 1996, according to MIT’s official biography of Zimmermann.
Separately, RSA Data Security accused Zimmermann of patent infringement for incorporating RSA’s encryption technique into PGP without a license, a dispute that was resolved in the late 1990s.
After the criminal case ended, Zimmermann founded PGP Inc., which was acquired by Network Associates Inc. in 1997, where he remained as Senior Fellow for three years. PGP was acquired by a new company, PGP Corporation, from Network Associates in 2002, and Zimmermann served as a special advisor and consultant until Symantec acquired PGP Corporation in 2010.
Since 2004, his work has focused on secure telephony over the internet, including the development of the ZRTP protocol. He co-founded Silent Circle, a secure communications company, and has served as Associate Professor Emeritus of cybersecurity at Delft University of Technology in the Netherlands.
For profiles of other builders shaping the industry, visit our crypto personalities page.
Philip Zimmermann’s Views and Positions
Zimmermann has consistently framed privacy as a natural right rather than a legal grant, arguing that pre-digital society afforded people private conversation by default. In one of his early notes introducing PGP, he wrote that two centuries ago “all conversations were private,” since anyone seeking privacy could simply step out of earshot, an option digital communication has entirely removed.
He has also drawn a distinction between the labor-intensive surveillance of the past and the scale of automated digital monitoring, once describing traditional mail interception as “catching one fish at a time, with a hook and line” compared to email surveillance, which he compared to “driftnet fishing.”
Zimmermann’s work is frequently cited as a foundational influence on the cypherpunk movement, the loose community of cryptographers and privacy advocates in the 1990s whose ideas about decentralized, government-resistant systems later informed Bitcoin’s design.
However, do note that PGP was not incorporated into Bitcoin’s code, but the broader intellectual case Zimmermann helped establish, that ordinary people have a right to strong encryption independent of government approval, is widely credited as part of the ideological groundwork that made Bitcoin’s cypherpunk framing possible. Readers new to Bitcoin’s underlying design can find the fundamentals in our guide on how Bitcoin works.
Philip Zimmermann in the News
Zimmermann’s case became one of the defining episodes of what is now called the “crypto wars” of the early 1990s, a series of conflicts between the US government and privacy advocates over encryption policy.
MIT came to his defense by publishing a 600-page book containing the PGP source code, effectively arguing that if Zimmermann was an illegal arms dealer, so was a leading American research university. The Electronic Frontier Foundation’s separate legal work during this period led to a 1995 court decision establishing that software code is a form of speech protected under the First Amendment.
More than two decades later, when journalists analyzed documents leaked by Edward Snowden in 2012, they found NSA records containing intercepted messages the agency had been unable to decrypt, marked only “No decrypt available for this PGP encrypted message.”
Frequently Asked Questions
Need a refresher? Here are the questions readers most often ask about Philip Zimmermann.
Who is Philip Zimmermann?
Philip Zimmermann is an American cryptographer best known as the creator of PGP, or Pretty Good Privacy, an email encryption program he released for free in 1991. The release led to a three-year federal criminal investigation, and his work is widely cited as a foundational influence on the cypherpunk movement that later shaped Bitcoin’s design.
How does PGP encryption actually work?
PGP uses public key encryption, a system that splits an encryption key into a public half and a private half. Anyone can use a recipient’s public key to encrypt a message, but only the recipient’s private key can decrypt it. This means a sender never needs to share a secret key in advance, solving the long-standing key distribution problem that made secure communication difficult before public key cryptography existed.
Why was Philip Zimmermann investigated by the federal government?
The US government classified strong encryption software as munitions under export law at the time, and Zimmermann’s free public release of PGP in 1991 made its way outside the United States. Federal investigators opened a three-year criminal investigation into whether this violated weapons-export restrictions, a case that could have resulted in prison time before the government dropped it in early 1996.
Did Philip Zimmermann help create Bitcoin?
Philip Zimmermann did not help create Bitcoin nor contribute code to it. His creation of PGP and his broader advocacy for strong, government-independent encryption are widely credited as part of the cypherpunk intellectual movement that shaped the philosophical case for Bitcoin, but PGP itself was not incorporated into Bitcoin’s design.
What happened to PGP after Philip Zimmermann’s legal case ended?
After the federal case was dropped in 1996, Zimmermann founded PGP Inc., which was acquired by Network Associates in 1997. PGP was later acquired by PGP Corporation in 2002 from Network Associates, where Zimmermann remained an advisor until Symantec acquired PGP in 2010.
