Introduction to PGP


Beginner's section

What is PGP?

I have set up this page in response to questions I get about PGP - what it is, where to get it, and how to use it.

PGP (short for Pretty Good Privacy), created by Philip Zimmermann, is the de facto standard program for secure e-mail and file encryption on the Internet. Its public-key cryptography system enables people who have never met to secure transmitted messages against unauthorized reading and to add digital signatures to messages to guarantee their authenticity.

Why do we need PGP? E-mail sent over the Internet is more like paper mail on a postcard than mail in a sealed envelope. It can easily be read, or even altered, by anyone with privileged access to any of the computers along the route followed by the mail. Hackers can read and/or forge e-mail. Government agencies eavesdrop on private communications.

Top secret documents from the US National Security Agency reveal the massive scale of government spying on our supposedly private communications.

More top secret documents from NSA and GCHQ revealing some of their dirty tricks to enable them to spy more effectively.

For further discussion of what PGP is for, and what it can do, read the following articles:

In a full transcript of an interview on the radio show High Tech Today Phil Zimmermann himself explains why he wrote PGP.

More detailed information about PGP, and copies of the program itself for various platforms, can be found from the links given below.

Basic tutorials for beginners

There is considerable overlap between these tutorials. If you don't find the information you need in one of them, try another, or try the FAQ. Some of these sites are out of date, referring only to older versions of PGP, but they still provide generally useful information.

Downloading PGP

The proliferation of different PGP versions can be rather confusing. The following links provide an explanation of the various versions and what they can do: An early version of PGP for MS-DOS can be downloaded directly from here:

PGP 2.6.3ia for RISC OS. Here you can find a collection of PGP software and other security utilities for RISC OS (Acorn) computers. There is also a RISC OS version of GnuPG, which is compatible with (and even superior to) modern versions of PGP.

Various versions up to PGP are available for many different operating systems, but not every version exists for every platform. Whichever operating system you use, you can find an appropriate version on one of the following sites:

Some PGP-related links

Although some of the following links are not up to date and lack information about the latest versions of PGP, they all provide useful general information.

The UKERNA Secure E-Mail Project

The United Kingdom Education and Research Networking Association (UKERNA) runs the Joint Academic Network (JANET) on behalf of the Academic Community of the U.K. (approximately UKERNA sees the current solution to authentication and privacy of documents to be PGP and is investigating how PGP can be made easy to use for sending e-mail.

How PGP works (in part)

If you are mathematically inclined and understand (or are willing to learn) a little about modular arithmetic, you can read about the maths behind some public-key cryptosystems at the following URLs:

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