Milburn

Steganography is what I would call the less powerful and less well known brother of cryptography. Whereas cryptography is encoding something so it can’t be read without a key, steganography is hiding something so it can’t be found without directions. Since cryptography offers a greater level of security for less effort it has often been used as opposed to steganography.

Think of cryptography as the lock to a safe. You need a key to open the safe. Steganography is hiding the safe somewhere where it can’t be found easily such as behind the painting on the wall. To find the safe you need directions. So how is steganography useful in the modern world. It can actually be used in several ways. A secret file can be hidden on your computer so it looks like an ordinary file. I’m going to show you today how to hide an MP3 file inside a JPEG or GIF image.

Firstly, we need two files to work with. Create a recording which you wish to hide and save it as an MP3 file then find an innocent GIF or JPEG. Size doesn’t matter but putting a 10MB MP3 file inside a 10×10 GIF image may look slightly wrong. Place your two images in the same directory.

Bring up the command prompt and navigate to the directory in which your files are saved using the cd command. Write the following command

copy /b wood.jpeg + rain.mp3 test.jpeg

Obviously change the file names in the example above. The /b stands for binary so the command prompt will make a binary copy of wood.jpeg and rain.mp3 and combine them in the file test.jpeg.

The file created will operate like a normal JPEG image until you change the extension to mp3 or run the file with a program which only supports MP3 files. This has many uses, you can email inconspicuous images to your friends for them to extract the file hidden within. This technique is not exclusive to MP3 files. You can hide whole zip files inside an image meaning one image can hide an unlimited number of files.

For additional security you could encrypt your files before hiding them inside an image. Steganography and cryptography combined is a powerful weapon against eavesdroppers and code breakers. If they don’t know where the encrypted message is they can’t tamper with it or decrypt it.