PGP

Here is my own PGP key. Fingerprint: 0D7D 527F 9268 F693 74BB A666 FD01 37F0 3362 7346
Once you’ve installed PGP, try sending me an encrypted message.

GNU Privacy Guard. Works on all operating systems. Quote “GnuPG is a complete and free replacement for PGP.” GUI: GPGshell, Windows Privacy Tray WinPT
Enigmail Using GPG together with Thunderbird
Mailvelope for web-based email systems

(image from http://imgs.xkcd.com/comics/pgp.png)