[3] From 2016 to 2021, he worked at Delft University of Technology as an Associate Professor in the Cybersecurity section at the Faculty of Electrical Engineering, Mathematics, and Computer Science.

[5] The United States Government had long regarded cryptographic software as a munition, and thus subject to arms trafficking export controls.

The investigation lasted three years, but was finally dropped without filing charges after MIT Press published the source code of PGP.

Zimmermann's introduction says the book contains "all of the C source code to a software package called PGP" and that the unusual publication in book form of the complete source code for a computer program was a direct response to the U.S. government's criminal investigation of Zimmermann for violations of U.S. export restrictions as a result of the international spread of PGP's use.

[3][8] In October 2013, Zimmermann, along with other key employees from Silent Circle, teamed up with Lavabit founder Ladar Levison to create the Dark Mail Alliance.

[9] He sees today's established social media platforms as a threat to democracy and privacy, because of their profit-oriented revenue models that "are all about exploiting our personal information" and "[deepen] the political divides in our culture", and hoped Okuna would help solve these problems.