Author's preface to the book: "PGP Source Code and Internals" (1995) (philzimmermann.com)

Philip Zimmermann’s 1995 preface explains why MIT Press published the full C source code of PGP and frames it as a civil-liberties issue tied to government efforts to restrict or control strong encryption. He recounts the controversies around the Clipper chip, FBI wiretap proposals, and export controls that affected PGP’s spread, including his own legal troubles. The preface also describes PGP’s cryptographic components and acknowledges the volunteer developers and legal teams behind the project.