GnuPG
Info
PGP encryption of email and files. Since PGP is not free GnuPG comes to the rescue.
Quote:
GnuPG is the GNU project's complete and free implementation of the OpenPGP standard as defined by RFC4880 . GnuPG allows to encrypt and sign your data and communication, features a versatile key management system as well as access modules for all kinds of public key directories. GnuPG, also known as GPG, is a command line tool with features for easy integration with other applications. A wealth of frontend applications and libraries are available. Version 2 of GnuPG also provides support for S/MIME.
More information: http://www.gnupg.org/
Installation
Archlinux
pacman -Sv gnupg pinentry
You should use gpg-agent to manage the interactions between your software:
gpg-agent is mostly used as daemon to request and cache the password for the keychain. This is useful if GnuPG is used from an external program like a mail client. It can be activated by adding following line in ~/.gnupg/gpg.conf:
use-agent
This tells GnuPG to use the agent whenever it needs the password. However, the agent needs to run already. To autostart it, create the following file and make it executable: