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.
You could also hide a second image inside the first.
What would make you suspect steganography?
Look at these files.
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:
- Can we determine that there is steganography in fileD?
- If there is, what was hidden in it?
We’ll explore this problem in the lesson LSB Steganography.