Introduction - If you have any usage issues, please Google them yourself
An Introduction To Cryptography
Chapter 1, “The Basics of Cryptography,” provides an overview of the
terminology and concepts you will encounter as you use PGP products.
Chapter 2, “Phil Zimmermann on PGP,” written by PGP’s creator, contains
discussions of security, privacy, and the vulnerabilities inherent in any
security system, even PGP.