Phil Zimmermann, PGP, and the Birth of Public Email Encryption

Why PGP Matters Beyond Email

PGP (Pretty Good Privacy) was a turning point: it made strong encryption something ordinary people could actually use, not just governments, banks, or university labs. Even if you never encrypted an email, PGP helped normalize the idea that privacy isn’t a special privilege—it’s a feature that software can and should provide.

Why email became the battleground

Email was (and still is) one of the most common ways to share sensitive information: personal conversations, legal details, medical updates, business plans. But early email was designed more like a digital postcard than a sealed envelope. Messages often traveled across multiple systems and sat on servers in readable form, and anyone with access to those systems—or the network paths between them—could potentially view or copy them.

PGP challenged that status quo by giving individuals a way to protect messages end-to-end, without asking permission from providers or relying on a single company to “do the right thing.” That shift—putting control in the hands of users—echoes through modern debates about secure messaging, software supply chains, and digital rights.

What this article will cover

We’ll look at the history behind Phil Zimmermann’s decision to release PGP, the core ideas that made it work, the controversy it triggered (including government pressure), and the long-term lessons for privacy and security tools today.

Key terms, in plain English

Encryption: scrambling information so only someone with the right secret can read it.

Keys: the pieces of information used to lock and unlock encrypted data. Think of them like digital locks and matching keys.

Signatures: a way to prove a message (or file) really came from a specific person and wasn’t altered—similar to signing a document, but verifiable by software.

Those concepts power more than email: they underpin trust, authenticity, and privacy across the modern internet.

Email Before PGP: A Privacy Problem Hiding in Plain Sight

By the late 1980s and early 1990s, email was spreading from universities and research labs into companies and public networks. It felt like sending a private letter—fast, direct, and mostly invisible. Technically, it was closer to a postcard.

Why email was insecure by default

Early email systems were built for convenience and reliability, not confidentiality. Messages often traveled through multiple servers (“hops”), and each stop was an opportunity for copying or inspection. Administrators could access stored mailboxes, backups captured everything, and forwarding a message was effortless.

Even when you trusted the person you wrote to, you were also trusting every machine in between—and every policy governing those machines.

“Just trust the network” stopped scaling

When email lived inside small communities, informal trust worked. As systems grew and interconnected, that assumption broke down. More networks meant more operators, more misconfigurations, more shared infrastructure, and more chances that a message would be exposed—accidentally or deliberately.

This wasn’t only about spies. It was about ordinary realities: shared computers, account compromises, curious insiders, and messages sitting unencrypted on disks for years.

A realistic threat model (no movie villains required)

Before PGP, common risks were straightforward:

• Snooping: someone reading messages in transit or from stored mailboxes and backups.
• Tampering: altering a message before it reached the recipient, sometimes subtly.
• Impersonation: sending mail that looked like it came from someone else, because identity checks were weak.

In short, email offered speed and reach, but little protection for privacy or authenticity. PGP emerged as an answer to that gap: making “private email” mean something concrete rather than hopeful.

Phil Zimmermann’s Goal: Privacy Tools for Ordinary People

Phil Zimmermann was a software engineer and long-time peace activist who worried about how quickly personal communications were becoming easy to monitor. His core belief was simple: if governments, corporations, and well-funded criminals could use strong cryptography, then ordinary people should be able to protect themselves too.

“Privacy isn’t only for the powerful”

Zimmermann didn’t frame PGP as a gadget for spies or a luxury feature for big companies. He saw private communication as part of basic civil liberties—especially for journalists, dissidents, human rights groups, and anyone living under the threat of surveillance. The idea was to make strong encryption practical for everyday use, rather than something locked behind institutional access or expensive enterprise tools.

Accessibility mattered as much as the algorithm

PGP’s impact wasn’t just that it used strong cryptography—it’s that people could actually get it.

In the early 1990s, many security tools were either proprietary, restricted, or simply hard to obtain. PGP spread because it was distributed widely and copied easily, showing how software distribution can be political: the more friction you remove, the more normal the behavior becomes. As PGP circulated through bulletin boards, FTP servers, and disk sharing, encryption stopped being an abstract academic concept and became something individuals could try on their own machines.

A documented outcome: encryption became a public expectation

Zimmermann’s stated motivation—putting privacy tools into public hands—helped shift encryption from a niche capability to a contested public right. Even among people who never used PGP directly, the project helped normalize the expectation that private communication should be technically possible, not merely promised by policy.

Public Key Cryptography, Explained Without Math

Public key cryptography sounds technical, but the core idea is simple: it solves the “how do we share a secret without already having a secret?” problem.

Two kinds of locks: shared-key vs public-key

Symmetric encryption is like having one house key that both you and a friend use. It’s fast and strong, but there’s an awkward moment: you have to get the key to your friend safely. If you mail the key in the same envelope as the message, anyone who opens the envelope gets everything.

Public key encryption uses a different analogy: a padlock that anyone can close, but only you can open.

• You publish the padlock (your public key).
• Anyone can snap it onto a box (encrypt a message to you).
• Only you have the unique key that opens it (your private key).

This flips the problem around: you don’t need a secure channel to hand out the “locking” part.

Why key sharing is still the hard part

Public key crypto avoids sharing a secret key upfront, but it introduces a new question: how do I know that public key really belongs to the person I think it does? If an attacker can trick you into using their public key, you’ll confidently encrypt messages straight to them.

That identity-checking challenge is why PGP also focuses on verification (later, the “web of trust”).

How PGP combines both for speed and practicality

PGP doesn’t usually encrypt long emails directly with public key methods. Instead it uses a hybrid approach:

1. PGP creates a one-time symmetric session key (fast).
2. It encrypts the message with that session key.
3. It encrypts the session key with the recipient’s public key (safe to share).

What encryption does—and doesn’t—protect

PGP can protect content and can prove who signed a message. It generally does not hide email metadata (like subject lines in some setups, timestamps, recipients), and it can’t defend you if your device or mailbox is already compromised.

How PGP Works in Practice: Keys, Encryption, and Signatures

PGP feels mysterious until you break it into three everyday ingredients: a keypair, encryption, and signatures. Once you see how those pieces fit, most of the “magic” becomes routine—like locking a letter, sealing it, and signing the envelope.

The keypair: your public lock and private key

A PGP keypair is two related keys:

• Public key: safe to share. People use it to encrypt messages to you.
• Private key: kept secret. You use it to decrypt those messages and to create signatures.

In email terms, your public key is the padlock you hand out; your private key is the only key that can open it.

Encryption vs. signatures: privacy vs. proof

PGP does two different jobs that are easy to mix up:

• Encryption (confidentiality) ensures only the intended recipient can read the content.
• Digital signatures (authenticity + integrity) prove the message was written by the holder of a specific private key and that it wasn’t altered in transit.

You can encrypt without signing (private but not strongly attributable), sign without encrypting (public but verifiable), or do both.

Common tasks: generating, sharing, and revoking

Most users end up doing a small set of recurring tasks:

• Generate a keypair, ideally protected with a strong passphrase.
• Share your public key (often via a keyserver or as an attachment) and import others’ public keys.
• Revoke keys when a device is lost, a private key might be exposed, or you’re rotating to a new key. Revocation is your “this key is no longer me” signal.

Typical failure modes to watch for

PGP usually fails at the human layer: lost private keys (you can’t decrypt old mail), unverified public keys (you encrypt to an impostor), and weak passphrases (attackers guess their way to your private key). The tooling works best when key verification and backups are treated as part of the workflow, not an afterthought.

The Web of Trust: Decentralized Identity Before Social Platforms

PGP didn’t just need a way to encrypt messages—it needed a way for people to know whose key they were using. If you encrypt an email to the wrong public key, you may be sending secrets to an impostor.

The identity problem it tries to solve

The “web of trust” is PGP’s answer to identity verification without a central authority. Instead of relying on a single company or government-run certificate provider to vouch for identities, users vouch for each other. Trust becomes something you build through human relationships: friends, colleagues, communities, meetups.

What it means to sign someone else’s key

When you “sign” another person’s public key, you’re adding your digital endorsement that the key belongs to that person (usually after checking an ID and confirming the key fingerprint). That signature doesn’t magically make the key safe for everyone—but it gives others a data point.

If someone trusts you, and sees you signed Alice’s key, they may decide Alice’s key is likely authentic. Over time, many overlapping signatures can create confidence in a key’s identity.

Strengths—and why it stayed hard

The upside is decentralization: no single gatekeeper can revoke access, silently issue a replacement key, or become a single point of failure.

The downside is usability and social friction. People must understand fingerprints, key servers, verification steps, and the real-world act of checking identity. That complexity affects security outcomes: when verification feels inconvenient, many users skip it—reducing the web of trust to “download a key and hope,” which weakens the promise of secure communication.

When Encryption Became Political: Export Controls and Pressure

PGP didn’t arrive in a neutral environment. In the early 1990s, the U.S. government treated strong cryptography as a strategic technology—closer to military hardware than consumer software. That meant encryption wasn’t just a technical feature; it was a policy problem.

Export controls, in plain terms

At the time, U.S. export rules restricted shipping certain cryptographic tools and “munitions” abroad. The practical effect was that software using strong encryption could be subject to licensing, limits on key strength, or outright barriers to international distribution. These policies were shaped by Cold War-era assumptions: if adversaries could easily use strong encryption, intelligence collection and military operations could become harder.

Why encryption was framed as a national security issue

From a national security perspective, widespread access to strong encryption raised a simple concern: it could reduce the government’s ability to monitor communications of foreign targets and criminals. Policymakers worried that once powerful encryption was broadly available, it wouldn’t be possible to “put the genie back in the bottle.”

Privacy advocates saw the same reality from the opposite angle: if everyday people couldn’t protect their communications, privacy and free expression would remain fragile—especially as more life moved onto networked computers.

How PGP challenged the status quo

PGP’s distribution model collided with these controls. It was designed for ordinary users, and it spread quickly through online sharing—mirrors, bulletin boards, and early internet communities—making it difficult to treat like a traditional exportable product. By turning strong encryption into widely available software, PGP tested whether old rules could realistically govern code that could be copied and published globally.

The result was pressure on developers and organizations: encryption was no longer a niche academic topic, but a public political debate about who should have access to privacy tools—and under what conditions.

The PGP Investigation and the Message It Sent to Developers

PGP didn’t just introduce email encryption to the public—it also triggered a government investigation that turned a software release into a headline.

What the investigation was about (in plain terms)

In the early 1990s, the U.S. treated strong encryption like a military technology. Shipping it abroad could fall under “export” rules. When PGP spread quickly—mirrored on servers and shared across borders—authorities opened a criminal investigation into whether Phil Zimmermann had illegally exported encryption.

Zimmermann’s basic argument was straightforward: he had published software for ordinary people, not weapons. Supporters also pointed out an uncomfortable reality: once code is online, copying it is effortless. The investigation wasn’t only about what Zimmermann intended; it was about whether the government could keep powerful privacy tools from circulating.

The signal it sent to builders of privacy tech

For developers and companies, the case was a warning: even if your goal is user privacy, you might be treated as a suspect. That message mattered because it shaped behavior. Teams considering end-to-end encryption had to weigh not just engineering effort, but legal exposure, business risk, and potential attention from regulators.

This is the “chilling effect” problem: when the cost of being investigated is high, people avoid building or publishing certain tools—even if they’re lawful—because the hassle and uncertainty alone can be punishing.

How media coverage shaped public understanding

Press coverage often framed PGP as either a shield for criminals or a lifeline for civil liberties. That simplified story stuck, and it influenced how encryption was discussed for decades: as a trade-off between privacy and safety, rather than a basic security feature that protects everyone (journalists, businesses, activists, and everyday users).

The investigation was eventually dropped, but the lesson remained: publishing encryption code could become a political act, whether you wanted it to or not.

The Modern Privacy Debate: What PGP Helped Ignite

PGP didn’t just add a new security feature to email—it forced a public argument about whether private communication should be normal for everyone, or reserved for special cases. Once ordinary people could encrypt messages on a personal computer, privacy stopped being an abstract principle and became a practical choice.

Privacy vs. public safety: the core tension

Supporters of strong encryption argue that privacy is a baseline right, not a privilege. Everyday life contains sensitive details—medical issues, financial records, family matters, business negotiations—and exposure can lead to harassment, stalking, identity theft, or censorship. From that view, encryption is closer to “lockable doors” than “secret tunnels.”

Law enforcement and security agencies often respond with a different concern: when communication is unreadable, investigations can slow down or fail. They worry about “going dark,” where criminals can coordinate beyond lawful reach. That anxiety is not imaginary; encryption can reduce visibility.

Encryption is not criminal intent

PGP helped clarify a key distinction: wanting privacy is not the same as planning harm. People don’t need to “prove innocence” to deserve confidentiality. The fact that some bad actors use encryption doesn’t make encryption itself suspicious—just as criminals using phones doesn’t make phones inherently criminal.

Defaults are policy

A lasting lesson from the PGP era is that design choices become political choices. If encryption is hard to use, hidden behind warnings, or treated as advanced, fewer people will adopt it—and more communication remains exposed by default. If secure options are simple and normal, privacy becomes an everyday expectation rather than an exception.

PGP’s Lasting Impact on Open Source and Software Integrity

PGP is often remembered as “email encryption,” but its bigger legacy may be how it normalized a simple idea in software: don’t just download code—verify it. By making cryptographic signatures accessible outside of military and academic circles, PGP helped open source projects develop habits that later became central to supply-chain security.

Signatures as a social contract

Open source runs on trust between people who may never meet. PGP signatures gave maintainers a practical way to say, “this release really came from me,” and gave users a way to check that claim independently.

That pattern spread into everyday workflows:

• Signing releases (tarballs, zip files, packages) so users can verify authorship
• Verifying downloads to detect tampering on mirrors, compromised servers, or man-in-the-middle attacks
• Signing commit tags and release notes to connect the “human identity” of a maintainer to a specific build

If you’ve ever seen a project publish a .asc signature alongside a download, that’s PGP culture in action.

Why public scrutiny mattered

PGP also reinforced something open source already valued: peer review. When tools and formats are public, more people can inspect them, critique them, and improve them. That doesn’t guarantee perfection—but it raises the cost of hidden backdoors and makes quiet failures harder to keep quiet.

Over time, this mindset fed into modern practices like reproducible builds (so others can confirm a binary matches its source) and more formal “chain of custody” thinking. If you want a gentle primer on that broader problem, this pairs well with /blog/software-supply-chain-basics.

A practical note for modern builders

Even if you build quickly using newer workflows—like vibe-coding platforms that generate full-stack apps from chat—you still benefit from the PGP-era discipline of verifiable releases. For example, teams using Koder.ai to spin up React frontends with a Go + PostgreSQL backend (and export the source code for their own pipelines) can still sign tags, sign release artifacts, and keep a clean chain of custody from “generated code” to “deployed build.” Speed doesn’t have to mean skipping integrity.

PGP didn’t solve software integrity on its own, but it gave developers a durable, portable mechanism—signatures—that still anchors many release and verification processes today.

Usability vs Security: Why PGP Stayed Powerful but Niche

PGP proved that strong email encryption could be put in the hands of ordinary people. But “possible” and “easy” are different things. Email is a decades-old system built for open delivery, and PGP adds security as an optional layer—one that users must actively maintain.

Why it never felt effortless

To use PGP well, you need to generate keys, protect your private key, and make sure contacts have the right public key. None of that is difficult for a specialist, but it’s a lot to ask of someone who just wants to send a message.

Email also has no built-in notion of verified identity. A name and address aren’t proof of who controls a key, so users must learn new habits: fingerprints, key servers, revocation certificates, expiration dates, and understanding what a “signature” really confirms.

The real-world pain points

Even after setup, everyday events create friction:

• Key verification: Comparing fingerprints in person or over another channel is secure, but it’s extra coordination.
• Device changes: New laptop, lost phone, or reinstalling an OS can mean migrating keys safely—or losing access to old encrypted mail.
• Support burden: When something breaks (wrong key, expired key, missing private key), there’s no “reset password” button. Friends become help desks.

How modern secure messaging changed expectations

Secure messaging apps typically hide key management behind the scenes, automatically syncing identity across devices and warning users when safety changes (for example, when a contact reinstalls the app). That smoother experience is possible because the app controls the whole environment—identity, delivery, and encryption—while email remains a loose federation of providers and clients.

What “good defaults” look like

Privacy-friendly tools succeed when they minimize decisions users must make: encrypt by default where possible, provide clear human-readable warnings, offer safe recovery options, and reduce reliance on manual key handling—without pretending verification doesn’t matter.

PGP Today: When to Use It, When to Choose Alternatives

PGP is no longer the default answer to private communication—but it still solves a specific problem better than most tools: sending verifiable, end-to-end encrypted email across organizations without needing both sides on the same platform.

Where PGP still fits

PGP remains useful when email is unavoidable and long-term traceability matters.

• Journalists and activists: communicating with sources who can’t install a new app, while still enabling encryption and identity verification.
• Compliance workflows: exchanging sensitive documents with partners via email in regulated environments where audit trails and key ownership are important.
• Archives and records: encrypting files meant to be stored for years, where you may need to prove who signed a message or document.

When other options may be better

If your goal is simple, low-friction private chat, PGP can be the wrong tool.

• Secure messengers (e.g., Signal-style systems) usually provide easier setup, contact verification, and safer defaults.
• Secure portals are often better for businesses sending documents to customers: fewer key-management mistakes and clearer access controls.

If you’re evaluating these options for a team, it helps to compare operational effort and support needs alongside cost (see /pricing) and review your security expectations (/security).

A simple checklist for adopting PGP responsibly

PGP failures are often process failures. Before rolling it out, confirm you have:

1. Training: basic concepts (public vs private keys, verifying fingerprints, signing vs encrypting).
2. Policies: when encryption is required, how keys are approved, and how to handle lost access.
3. Backups and recovery: protected key backups, clear ownership, and a plan for staff departures.
4. Key hygiene: expiration dates, rotation rules, and revocation certificates stored safely.
5. Verification practice: a consistent way to confirm identities (not just “I got your key in an email”).

Used thoughtfully, PGP is still a practical tool—especially where email is the only common denominator and authenticity matters as much as secrecy.