Re: can you tell me the basic of chaos image encryption

G’day!
   Hmmm...chaos image encyption, eh? Might you be referring to 
steganography, then?

   Steganography takes one piece of information and hides it within 
another. Computer files (images, sounds recordings, even disks) contain 
unused or insignificant areas of data. Steganography takes advantage of 
these areas and replaces them with hidden information (like encrypted e-
mail). The files can then be exchanged without anyone knowing what really 
lies inside of them. An image of the space shuttle landing might contain a 
private letter to a friend. A recording of a short sentence might contain 
your company's plans for a secret new product. Steganography can also be 
used to place a hidden "trademark" in images, music, and software, a 
technique referred to as watermarking. 

   Computer steganography is based on two principles. The first one is 
that the files that contain digitized images or sound can be altered to a 
certain extent without losing their functionality, unlike other types of 
data that have to be exact in order to function properly. The other 
principle deals with the human inability to distinguish minor changes in 
image color or sound quality, which is especially easy to make use of in 
objects that contain redundant information, be it 16-bit sound, 8-bit or 
(even better) 24-bit image. Speaking of images, changing the value of the 
least significant bit of the pixel color won’t result in any perceivable 
change of that color.

   One can tell the difference between the clean and the loaded file only 
by comparing them, so if you look at the resulting file only, it looks 
totally innocent. For better security it is recommended that one uses 
images with many halftones and preferably unknown to the public because 
minor changes in them will not be noticed. Using Henri Matisse's The Dance 
is not a very good idea, because everyone knows what it looks like (at 
least in Europe). Besides, there are large spots of the same color. Try 
using the picture of you and your friend hiking in the woods instead if 
you are encoding information inside a picture.

   I hope this helps you...

   Be seeing you...
   Steve Cartoon
   Web Engineer, Edmark.com

PS: Try this website for more information and software on steganography:
 http://www.isse.gmu.edu/~njohnson/Steganography/

   I guarantee you will find more information than you probably will ever 
remember on the subject. I certainly did!