Steganography

What is Steganography

Steganography is defined by Merriam-Webster as the art or practice of concealing a message, image, or file.

Different Types of Steganography

There are many different types of Steganography. However, they all share the same goal of hiding the presence of some particular piece of data.

Micro Dots

Micro dots are used to shrink the physical size of a document or image. This technique was used heavily during World War I and World War II. A person wanting to send data secretly to another person would need to use something called a Micro Dot Camera to take a picture of thing they want to send. Once they have the picture the Micro Dot would then either be applied to a document and mailed, or just attached to a carrier pigeon. Of course you would want to make sure the document has some information on it that someone could easily read, otherwise they might suspect you are trying to hide something from them. Sizes of the various types of Micro Dots differ due to the wide variety of applications. Currently, they are being sprayed onto laptops and car parts to try and stop reselling of the equipment.

Null Ciphers

Null Ciphers are even probably one of the simpler forms of steganography. All it requires is a pre-shared key that both the sender and receiver know. Here is an example of a null cipher:

PRESIDENT'S EMBARGO RULING SHOULD HAVE IMMEDIATE NOTICE. GRAVE SITUATION AFFECTING INTERNATIONAL LAW. STATEMENT FORESHADOWS RUIN OF MANY NEUTRALS. YELLOW JOURNALS UNIFYING NATIONAL EXCITEMENT IMMENSELY.

Take the first letter of each letter of each word and you get PERSHINGSAILSFROMNYJUNEI which is PERSHING SAILS FROM NY JUNE I after you apply spaces.

Hiding Data in an Image

Hiding data in images is probably the most prevalent form of Steganography used today. It is rumored that terrorist organizations use this technique to spread information to its members. When someone wants to hide something in an image, they use a program specifically designed to do it. The program typically changes insignificant pixels in the image that are relatively unnoticeable by most people. It also helps if the image you use is original. If you go online and get an image, modify it, and hide something in it, a person using some software could easily find the differences between the two. Encrypting the data before you hide it would also be a good idea just in case it is ever found out that there is data hidden in the image.

Programs Associated with Steganography

• Steghide
  • An opensource program used on Linux and Windows systems to hide data in either an image or an audio file.
  • http://steghide.sourceforge.net/

• For a complete list of stego tools please click on the following link:
  • http://www.jjtc.com/Security/stegtools.htm

How to Hide Data in an Image

1. Download JPHS for Windows at http://linux01.gwdg.de/~alatham/stego.html.
2. Unzip it and run jphswin.exe.
3. Agree to the End User Agreement
4. Open the jpeg you want to use as the carrier image (the one that will hold the data) by clicking "Open jpeg" on the top toolbar.
5. Click "Hide" on the top toolbar and put in a secret pass-phrase (remember the person you intend to receive the file also needs to know this key).
6. Select the file you wish to hide and click ok. If a message pops up warning you that your selected file is too large, either find a bigger carrier image or find a smaller file to hide.
7. Click either "Save" or "Save as" on the top toolbar and you are done.

How to get Data out of an Image

This picture has another picture file hidden in it.

1. Download the full-resolution copy of this picture.
2. Open JPHS for Windows.
3. Open the downloaded image by clicking "Open jpeg"
4. Click "Seek"
5. When it asks you where to save the file, make sure to save it as a jpg. Normally you would know in advance exactly what type of file the sender is giving you.