Philip R. Zimmermann wrote the essay in Boulder, Colorado, in June 1991. It appeared in the original 1991 PGP User’s Guide and received an update in 1999. A quotation attributed to Mahatma Gandhi opens the text. Zimmermann’s central claim is that private communication belongs to ordinary people, regardless of what they are discussing.

He points to political campaigns and tax matters as everyday reasons for confidentiality. He also mentions intimate relationships and contact with dissidents living under repressive governments. The U.S. Bill of Rights implies a right to privacy, he argues, while the country’s founders had little reason to spell out private conversation when physical eavesdropping required someone to be nearby.

Telephones and the internet changed that situation. Cellular calls could be monitored with radio equipment, and email travelled across networks with comparable exposure. Earlier surveillance of paper mail or telephone calls demanded considerable labor, which limited its scale. Computers could scan huge volumes of email for keywords automatically. Increasing computing power would make similar analysis possible for voice traffic.

Zimmermann compares routine encryption with using envelopes for postal mail. Universal use would reduce the attention drawn by any one person protecting a message. That social effect matters because privacy becomes harder to criminalize when it is ordinary practice.

Senate Bill 266, a 1991 omnibus crime bill, contained a non-binding resolution supporting government access to encrypted communications. Its proposed policy would have pushed makers of secure communications equipment to provide plaintext access to voice and data when legally authorized. Zimmermann says the measure prompted him to publish PGP electronically and free of charge that year. Vigorous opposition from civil-liberties groups and industry helped defeat it.

The 1994 Communications Assistance for Law Enforcement Act, known as CALEA, required phone companies to add remote wiretap capabilities to digital switching offices. Court authorization remained necessary for a tap, but the infrastructure would make interception possible from government offices without physical access to a telephone line. Zimmermann warns that surveillance systems can last for generations while laws and political conditions can change quickly.

In 1995, the FBI disclosed plans for phone companies to support simultaneous interception of 1 percent of all calls in major U.S. cities. That would have exceeded the roughly 1,000 court-authorized wiretaps carried out each year across federal, state, and local levels by more than a thousandfold. Zimmermann saw automated speech recognition as the only plausible way to process such a volume, with searches for keywords or particular voices. The agency said the capacity was needed for future planning. Congress rejected the proposal.

The essay extends the threat beyond government. Business competitors, organized crime, and foreign intelligence services could target confidential communications. Zimmermann notes that some foreign governments acknowledged using signals intelligence to aid companies from their own countries. U.S. restrictions on cryptography during the 1990s, he argues, also weakened American businesses against those threats.

In April 1993, the Clinton administration announced an encryption initiative developed at the NSA since the beginning of the Bush administration. Its centerpiece was the Clipper chip, which used a classified NSA algorithm. Each chip received a unique key during manufacture, while the government kept a copy in escrow. AT&T incorporated Clipper into secure voice products. Officials presented the system as voluntary and promised access only with legal authorization.

The computer industry opposed Clipper. FBI Director Louis Freeh said in 1994 that his agency would seek legislation if government-controlled cryptography lost access to communications. After the Oklahoma City bombing, Freeh told the Senate Judiciary Committee that public access to strong cryptography should be restricted, although nobody had claimed that the bombers had used it.

Zimmermann cites COINTELPRO surveillance of antiwar and civil-rights groups, the wiretapping of Martin Luther King, Nixon’s enemies list, and Watergate as evidence that official powers can be abused. He also refers to Internet laws that restricted civil liberties, the collection of confidential FBI files on Republican civil servants by parts of the Clinton White House, and aggressive investigations into the sexual conduct of political opponents.

During the 1990s, his answer was broad public use of strong cryptography while it remained legal. He believed widespread use would make a ban politically harder. In late 1999, the Clinton administration substantially abandoned U.S. export controls on cryptographic technology. Strong encryption could then be exported without an upper strength limit. Zimmermann considered that a victory on export policy, while calling for continued protection of domestic use and wider deployment against online surveillance. PGP, he concludes, gives individuals direct control over their privacy.