02 Steganography Overview

Topic Progress:

What is it?

Steganography is the act of hiding messages or data inside normal, unhidden messages or data.

For example, you could send a picture of a cat to a friend and hide text inside. Looking at the image, there’s nothing to make anyone think there’s a message hidden inside it.

Cat Picture with Steganography Text

You could also hide a second image inside the first.

Cat Picture with Steganography Image

What would make you suspect steganography?

Look at these files.

78 68 103 103 78 106 85 103 78 122 107 103 77 106 65 103 78 68 81 103 78 106 85 103 78 106 69 103 78 109 77 103 78 106 85 103 78 122 73 103 77 122 73 103 77 122 65 103 77 122 69 103 77 109 77 103 77 71 81 103 77 71 69 103 78 68 107 103 77 106 65 103 78 122 99 103 78 106 69 103 78 122 77 103 77 106 65 103 78 122 81 103 78 106 103 103 78 106 107 103 78 109 85 103 78 109 73 103 78 106 107 103 78 109 85 103 78 106 99 103 77 109 77 103 77 106 65 103 78 106 103 103 78 109 89 103 78 122 99 103 77 106 65 103 78 109 81 103 78 122 85 103 78 106 77 103 78 106 103 103 77 106 65 103 78 106 85 103 78 122 103 103 78 106 69 103 78 106 77 103 78 122 81 103 78 109 77 103 78 122 107 103 77 106 65 103 78 106 69 103 78 122 73 103 78 106 85 103 77 106 65 103 78 122 99 103 78 106 85 103 77 106 65 103 78 106 99 103 78 106 85 103 78 122 81 103 78 122 81 103 78 106 107 103 78 109 85 103 78 106 99 103 77 106 65 103 78 106 89 103 78 109 89 103 78 122 73 103 77 106 65 103 78 122 81 103 78 106 103 103 78 106 85 103 77 106 65 103 78 122 81

FileA

FileB

FileB

FileC

FileC

FileD

FileD

FileA and fileD appear the same, but they’re different. Also, fileD was modified after it was copied, so it’s possible there might be steganography in it.

FileB and fileC don’t appear to have been modified after being created. That doesn’t rule out the possibility that there’s steganography in them, but you’re more likely to find it in fileD. This brings up two questions:

  1. Can we determine that there is steganography in fileD?
  2. If there is, what was hidden in it?

We’ll explore this problem in the lesson LSB Steganography.