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Issue 20.5 ('Xojo Workflows')
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Exploring Steganography, Part 2

Retrieving a Picture in a Picture

Issue: 20.5 (September/October 2022)
Author: Eugene Dakin
Author Bio: Eugene works as a Senior Oilfield Technical Specialist. He has university degrees in the disciplines of Engineering, Chemistry, Biology, Business, and a Ph.D. in Chemical Engineering. He is the author of dozens of books on Xojo available on the xdevlibrary.com website.
Article Description: No description available.
Article Length (in bytes): 21,776
Starting Page Number: 15
Article Number: 20503
Resource File(s):

Download Icon project-20503.zip Updated: 2022-08-31 23:28:49

Related Link(s): None

Excerpt of article text...

In this article we will retrieve a picture hidden inside another picture, known as digital image steganography. An example program has been created in native Xojo code to retrieve the final hidden picture. This article and example explicitly works with LSB (Least Significant Bit) Steganography.

Steganography is the ability to hide and retrieve text, an image, or other data that is a secret, into a picture that is not a secret. Steganography also works by attempting to conceal that a secret message even exists.

Steganography occurs in the world of spies, hackers, and other activists. One of many legal areas where Steganography exists is when selling online pictures and a hidden watermark is added. If you download or attempt to copy a picture, there are deliberate hidden messages in the picture to record who downloaded the picture.

How to hide the message using the Xojo programming language without anyone knowing that a message was actually embedded was covered in Part 1. Today in part 2 we will show how to retrieve the hidden picture.

Our example uses an original PNG image, and the lowest color bit will be retrieved that will contain the information of the picture that was hidden. Changing the LSB in the original picture has an almost unnoticeable change to the image.

(An example of this type of manipulation would be to have a large number—such as 1,856,450—and change the last two digits to have the final value 1,856,497. The effect will be minimal. The original number is so large, that slightly changing the last two digits has a negligible effect on the overall value. The hidden image was placed into the original image by changing the last two digits of many bytes in the original picture.)

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