What is this for?
The issue of data privacy is increasing in importance. I don't like it when unauthorized people get access to my personal items; I doubt you like it either. And let's not forget the government. Much to the chagrin of those who believe in stripping people's identity and stealing their private thoughts, something can be done.
What can we do?
Use an encryption program like PGP, or, if you prefer open-source, free software (like I do), use GnuPG. Most Linux distros come with it so you don't have to do anything special to use it. If you are on Windows, like I am, you can use Gpg4Win.
How does it work?
GnuPG/PGP uses public-key cryptography for encryption. If you want to send something to J. Random User, you get their public key from a directory or from the recipient directly. The software then encrypts your e-mail using their public key. You can't run the process backwards using their public key to decode it; it can only be decrypted by the corresponding private key. This solves the problem with earlier encryption systems: that the same key is used for encryption and decryption. With this system, a user can put his public key out in the open for everybody to use.
This method can also be used to verify a signature. Say I send somebody an e-mail and sign it with my private key. If my public key can then verify the message successfully, then the recipient knows that I sent it, not somebody pretending to be me. Very nice.
Now what?
Now that you have GnuPG, you need my public key. Keys are in a special format known as Base64 encoding to ensure that the binary data isn't garbled in transmission since it is converted to alphanumeric data. All you need to do is cut and paste in order to import the key onto your keyring. My latest key is fingerprint 0x148F8259C3D1415D25BBA91D97E33ADA2023F486, below.
This key should be on most, if not all, available keyservers by searching for my name or e-mail address.
Note: Several of my previous keys have been revoked, have expired, or are no longer in use. This includes Key IDs: 0xAC053980, 0x3F96B56F (Revoked), 0x410CCD71, 0x40696B40 (Revoked), 0xEE915B05 (Revoked), and most recently 0x52AE6AB0 (Revoked). Do not use these keys.
That's it. Enjoy.