Introduction
Steg Studio is an image steganography software: it hides information in image files. You can do this by altering the least significant bit of the pixel bytes in an image. This changes the image in a way that may not be (too) noticeable to the human eye.Background
I did this projects some years back (2011) but my newly found love for open source has led me to release it. I altered some statements dealing with license and copyright to make it more permissive but I didn't change much in the code (except for adding support for password and putting classes in the Karabow.Steg.* namespaces), so the codes you will see are codes from many years back.Also, I would like to acknowledge that I got the bulk of my steganography code from my classmate back in 2011. I am absolutely sure he got the source code from somewhere/someone else. I have since lost contact with this ex-mate of mine and, as a result, had no name to include in the acknowledgement that appears in the source code (Karabow.Steg.Core/Steganographer.cs).
This is not one of my most original works. I will be writing on more projects soon enough but for the time being you can check out my favourite project of the moment,Quic web development framework. This post, however, helps me to "test the waters" as I'm about to dive deep into the world of open source development.
A Brief on Steganography
To hide information in an image, you can do this by altering the least significant bit of the pixel bytes in an image. This changes the image in a way that may not be (too) noticeable to the human eye.An image consists of a pixels, and each pixel has 3 colour components: R (red), G (green), B (blue). Each colour component is of the bytes data-type, which means it consists of eight bits (binary digits). The least significant bit is the one to the right, and this is the bit we alter.
So to hide a file in an image, we break that file into its constituent bits. That is, we get a representation of the file that consists of ones and zeros.
Now, we go through the pixels of the "mask image", and store the bits of the file in the least significant bit of each colour component of each pixel. Since a pixel has 3 colour components, it means you can store 3 bits per pixels. So a file that is 1000 bytes in length, which is 8000 bits, will require an image with at least (8000/3) pixels, approximately 2667 pixels. The pixels of a bitmap can be gotten by multiplying its width by its height. It should also be mentioned that a pixel has a fourth component, A (alpha), which represents its transparency/opacity. Including this component increases the amount of bits the image can store, since it now stores 4 bits per pixel, as against 3 bits per pixel.
For actual code you can check out Karabow.Steg.Core/Steganographer.cs. For more information you can always search online :).
How to use Steg Studio
System Requirements
- The particular build was built on a Windows 8 machine, but should run with no modification on Windows 10, Windows 7.
- The target framework is .NET Framework 4.5, but the source code can be built against .NET Framework 5.0 and many previous versions.
Using the App
I am assuming you have downloaded and built the relevant files.
- The "Encryption Page" is quite straightforward. You can select a file you want to hide, or a list of files using wild card characters (like *.txt), the image in which they will be hidden, and the password (without which the original files cannot be extracted from the image).
- Below is the folder from which I selected the files to hide. Visible also is the mask image, Mask.jpg.
Below is the same folder after I have hidden all the *.cs files in the mask image, Mask.jpg. Steg Studio saves the produced images with the same name as the original files, but with the same extension of the mask image.
I changed Mask.jpg to Mask.jpeg so that during the reverse process (getting the original files from the images), I can use the wild card *.jpg to get all appropriate images. - The "Decryption Page" is even simpler.
During "decryption", you have to supply a name with which the file extracted from the image will be stored. - Below is the folder after I have extracted all the hidden files from the appropriate images.
I did not choose to delete the "carrier" images. - Comparing the files before and after the entire process, you see that the final files are exactly identical to the original files.
Compare the file sizes.
