Practical CTF Steganography: Intro

Chapters

1. Intro

2. General

   1. Metadata
   2. File within the file

3. Audio

   1. Message hidden in spectrum

4. Text

   1. Zero-Width Steganography
   2. Base64 Padding

5. Image

   1. Message hidden in least significant bits (LSB)
6. List of tools

What is steganography?

According to the wikipedia it’s the practic of concealing a message within another message or a physical object. In computing/electronic contexts, a computer file, message, image or video is concealed within another file, message, image or video.

Unlike the cryptography, in steganography secret message presence is not obvious and doesn’t attract attention to itself. Both techniques combined together can be very difficult for unauthorized persons to compromise the message.

Steganography in terms of CTF challenges

There’s a big chance, that during CTF events one of the category will be Steganography (abbrv. Stego, Stegano etc.). Most of challenges involve retrieving flag from image, sound or document files. I have a doubt that I’m able to cover all possible techniques. But at least I’ll try to gather as much as I can with real-CTF examples.