"GnuPG, the GNU Privacy Guard, is the open source equivalent to
PGP, or Pretty Good Privacy, which has been available for Windows,
DOS, and some other operating systems for many years. It has all
the same features, based on the OpenPGP standard. The uses for
GnuPG (or GPG) are varied: It can be used to encrypt email messages
and files, or to digitally sign email messages and files. The first
use is obvious, encrypting emails or files on your hard drive
maintains the privacy and integrity of sensitive messages or
documents. The latter is extremely useful to maintain the integrity
of messages and files, especially when transmitting over insecure
networks. It certifies that a) the email was sent by whomever
claims to have sent it, and b) that a file has not been tampered
with.
"Using GPG is very easy and straightforward. It is a text-based
command line tool, but there are frontends to GPG that make it even
easier to use. The whole premise of GPG is PKI, or Public Key
Infrastructure. What this means is that GPG is based upon a two-key
system, a private key used to sign and decrypt, and a public key
used to decrypt and verify..."
