Symmetric encryption app

Truecrypt only creates encrypted volumes and then reads them. I use them all the time between OS X and XP. I have a portable version on my thumbdrive, and keep install apps along with the activation keys for them, in the encrypted volume. Mount them on the PC I am installing them on, and install. This works great. I have not tried the binary for Linux, but he OS X and XP versions work great. I have installed Office 2003 multiple times in this fashion, and not had any problems.

 

GPG is a cross platform, open source (GPL) - OS X, Linux, Windows et al. supporting symmetric encryption on single files e.g.:

gpg --symmetric

http://macgpg.sourceforge.net/

http://www.gpg4win.org/

And for the main site:

http://www.gnupg.org/

There are many examples if you hit Google - this may start you in the right direction:

http://www.screenage.de/blog/2008/06/19/my-package-of-the-day-gpg-for-symmetric-encryption/

And a cheat sheet...

http://charleslockhart.com/technical/gpg-cs.html

There are a slew of plugins for most popular mail clients, browsers and many other apps too...

Hope this helps!