Pretty Good Privacy (PGP) is an e-mail encryption scheme that has become a de facto standard. Its Web site serves more than a million pages a month to users in 166 countries [PGPI 2012]. Versions of PGP are available in the public domain; for example, you can find the PGP software for your favorite platform as well as lots of interesting reading at the International PGP Home Page.
When PGP is installed, the software creates a public key pair for the user. The public key can be posted on the user’s Web site or placed in a public key server. The private key is protected by the use of a password. The password has to be entered every time the user accesses the private key. PGP gives the user the option of digitally signing the message, encrypting the message, or both digitally signing and encrypting.