Tuesday, December 1, 2009

Steganography (using steghide)

Steganography is the ability to hide data in plain site. Hidden messages are hidden in such a way that no one other than the sender and the intended recipient should be aware of its existence. What that means is the picture that someone may have sent to you and a few other people could possible contain a hidden message and possibly only one or two of the recipients may know of its existence.

Steghide is a steganography program that has the ability to hide data in various image and audio file formats. The embeded data can be compressed and encrypted. Some supported file formats are JPEG, BMP, WAV and AU. There are no restrictions on the format of what the secret data should be. It runs on both Windows and linux OS's

Create a text file and type something in it that you wish to hide[name it confidential.txt].

Next, locate a jpg or bmp file that you would like to use as the cover file to hide the text file into.
When you get your image file run this command to test its storage capacity:
# steghide info image_file.jpg

Next lets embed our confidental.txt in the image file. By default, the embeded data would be encrypted with rijindale(aes - 128 bit) encryption in cbc mode. Note you would have to enter a password.
# steghide embed -cf image_file.jpg -ef confidential.txt

To extract the file run the following command then enter the password:
# steghide extract -sf image_file.jpg

Thats all to it.

"-cf": cover file to use
"-ef": file we want to hide
"-sf": this is the name of the stego file that we have created
"-e": specify encryptionto use if the default doesnt suit you.

To find out about the other encryption algorithms that you can use type:
# steghide encinfo

Resources/Good reading:

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