How to unmosaic/uncensor pictures

Can anyone give me a tutorial on how to uncensor/unmosiac pictures ?  I'm using The Gimp as a image editor.

You can recreate a mosaiced picture if it's a simple image, like a mosaiced credit card. If you use the exact same technique on an exactly same image, the end result will be the same. All you have to do is to write a script that iterates through all the possibilities and then compare it to the original. If you get a match you have a succesful unmosaiced picture...

Somehow I doubt you can do this...