Editing Pretty Good Privacy (section)

===Criminal investigation===
Shortly after its release, PGP encryption found its way outside the [[United States]], and in February 1993 Zimmermann became the formal target of a criminal investigation by the US Government for "[[United States Munitions List|munitions]] export without a license". At the time, cryptosystems using keys larger than [[40-bit encryption|40 bits]] were considered munitions within the definition of the [[Export of cryptography in the United States#PC era|US export regulations]]; PGP has never used keys smaller than 128 bits, so it qualified at that time. Penalties for violation, if found guilty, were substantial. After several years, the investigation of Zimmermann was closed without filing criminal charges against him or anyone else.

Zimmermann challenged these regulations in an imaginative way. In 1995, he published the entire [[source code]] of PGP in a hardback book,<ref name="zimmermann2">{{cite book |last= Zimmermann |first= Philip |author-link= Phil Zimmermann |title= PGP Source Code and Internals |year= 1995 |publisher= [[MIT Press]] |isbn= 0-262-24039-4}}</ref> via [[MIT Press]], which was distributed and sold widely. Anybody wishing to build their own copy of PGP could cut off the covers, separate the pages, and scan them using an [[Optical character recognition|OCR]] program (or conceivably enter it as a [[type-in program]] if OCR software was not available), creating a set of source code text files. One could then build the application using the freely available [[GNU Compiler Collection]]. PGP would thus be available anywhere in the world. The claimed principle was simple: export of ''munitions''—guns, bombs, planes, and software—was (and remains) restricted; but the export of ''books'' is protected by the [[First Amendment to the United States Constitution|First Amendment]]. The question was never tested in court with respect to PGP. In cases addressing other encryption software, however, two federal appeals courts have established the rule that cryptographic software source code is speech protected by the First Amendment (the [[United States Court of Appeals for the Ninth Circuit|Ninth Circuit Court of Appeals]] in the [[Bernstein v. United States|Bernstein case]] and the [[United States Court of Appeals for the Sixth Circuit|Sixth Circuit Court of Appeals]] in the [[Junger v. Daley|Junger case]]).

[[Export of cryptography in the United States#PC era|US export regulations]] regarding cryptography remain in force, but were liberalized substantially throughout the late 1990s. Since 2000, compliance with the regulations is also much easier. PGP encryption no longer meets the definition of a non-exportable weapon, and can be exported internationally except to seven specific countries and a list of named groups and individuals<ref>{{cite web |title=Lists to Check |url=https://www.bis.doc.gov/complianceandenforcement/liststocheck.htm |work=US Department of Commerce, Bureau of Industry and Security |access-date=December 4, 2011 |archive-url=https://web.archive.org/web/20100112230807/https://www.bis.doc.gov//complianceandenforcement/liststocheck.htm |archive-date=January 12, 2010 |url-status=dead }}</ref> (with whom substantially all US trade is prohibited under various US export controls).

The criminal investigation was dropped in 1996.<ref>{{cite web |last1=Zimmermann |first1=Phil |title=Significant Moments in PGP's History: Zimmermann Case Dropped |url=https://philzimmermann.com/EN/news/PRZ_case_dropped.html |website=philzimmermann.com |quote=The U.S. Attorney's Office for the Northern District of California has decided that your client, Philip Zimmermann, will not be prosecuted in connection with the posting to USENET in June 1991 of the encryption program Pretty Good Privacy. The investigation is closed. |access-date=February 16, 2024 |archive-date=October 5, 2024 |archive-url=https://web.archive.org/web/20241005182852/https://philzimmermann.com/EN/news/PRZ_case_dropped.html |url-status=live }} &ndash; page also contains NPR morning radio recording on this matter</ref>