Cryptography: why modes matter, and why 'encrypted' is not always 'unreadable'

You should give proper attribution for your images.

http://en.wikipedia.org/wiki/File:Tux.jpg

http://en.wikipedia.org/wiki/File:Tux_ecb.jpg

http://en.wikipedia.org/wiki/File:Tux_secure.jpg

Fair point, attributions modified.