PGP

Pretty Good Privacy (PGP) is probably the most used cryptographic software in the world.

PGP was implemented by Philip Zimmermann during the Cold War. Philip started planning to take his family to New Zealand because he believed that, in the event of a nuclear attack, the country, so isolated from the rest of the world, would be less impacted by atomic devastation. At some point, while planning to move to New Zealand, something changed his mind and he decided to remain in the US.

To communicate with his friends, Zimmermann, who was an activist in the anti-nuclear movement, developed PGP to secure messages and files transmitted via the internet. He released the software as open source, free of charge for non-commercial use.

At the time, cryptosystems larger than 40 bits were considered to be like munitions. Even today, cryptography is still considered a military weapon. There is a license that you must obtain if you decide to patent a new cryptosystem: you must have...