Modern steganographic methods include embedding
electronic communications, such as a text message or an
image, within another text message or image. Additionally,
the message can also be encrypted to further conceal its
content. For a successful encoding, a good cover medium
must be utilized. For electronic steganography over the
Internet, images are good candidates for cover medium. This
is because a cover medium must contain enough information
to hide the underlying message while subsequently not appearing
to have been modified. It is also desirable for the cover
medium to be common enough so as to not attract attention.
Images on the Internet are both ubiquitous and can be created
to contain enough cover information to hide the underlying
A simple example of using images to steganographically
hide a message is to modify the least significant bits of
an image to encode the message. By modifying the least significant
bit, the original image and the modified image appear identical
to the human visual systems. The altered image can be sent
via email to the intended recipient or posted on web sites
for recipients to download. Only persons who have knowledge
of the hidden message will be able to decode and recover
it. Although this method appears to work well, a simple
statistical analysis of the image will usually reveal that
additional information is hidden within it.
This simple form of steganography is what
we employed when we went about creating our program. We
allow the user to specify an input image and a text file
containing the secret message and then the program combines
the two and outputs another image that is virtually indistinguishable
from the original.
In recent years, more sophisticated techniques
of steganography have evolved, specifically for the purpose
of defeatin most standard methods of detecting steganography.
These involve analyzing the image prior to embedding the
message to determine its statistical properties. By locating
redundant bits of an image and probabilistically replacing
the redundant bits with new information, one can defeat
most basic statistical analyses. In addition, by subsequently
modifying other portions of the image, one can recreate
the "statistical" footprint of the original unmodified
image that can thwart most attempts at statistical analysis.
If we had the time we would investigate
ways of adapting our program to circumvent these detection
schemes but due to time constraints and the success of our
first iteration we decided to stop here. If wanted, there
are many freeware steganographic tools are readily available
on the Internet. Most of these have easy to use point and
click interfaces that enable a user to quickly encode information.
Steganographic tools available on the Internet range from
"StegFS" a free steganographic file system to
Windows based tools such as "S-Tools", OutGuess,
JSteg and JPHide to embed information within images.
[ Back ] [ Next