If you are looking for a secure way to email or
send files to people that you choose, then PG is the answer. At
this time, it is the most secure public encryption program
available for "legal" use.
PGP works by using a public and a private key. Your friends give
you their public key, and likewise, you give them yours. Messages
are encrypted with your public key and then decrypted with the
recipients private key. To keep things even more secure, the
private key itself is encrypted using a password, and can only be
unlocked by this method. The key lengths are quite large, ranging
from either 256, 512, 1024 or 2048 random bit keys, 2048 bits
being the most difficult to break. To use PGP, you need a good
working knowledge of UNIX command line switches, and you really
need to fully digest the README file first.
PGP is a great tool if you want to stop the NSA from reading your
email. Frankly, however, if the NSA does want to read your email,
then you've got more problems than we can help you with ! NB:
This is the INTERNATIONAL version. You cannot use this version in
the US. Exporting PGP 5 (The Windows 95 version) outside of the
United States is against U.S. Statute 22USC 2778, "Control
of Arms, Exports & Imports." (Yes, PGP is so powerful
it's classed as a weapon.)