Boy thinking with coloured light and code background

Operation Decode

Mission One: Obfuscation

There are many ways of encrypting data, but no matter what method you use, the end goal is always the same… to make information harder to access. One of the easiest ways to do this is simply to make the information harder to see by hiding it. This is called Obfuscation.

Steganography is the practice of concealing information inside other non-secret text or images. Red Reveal is one example of steganography. In this method, the information to be kept secret is written in a pale blue colour which is then hidden underneath a red pattern. To the casual observer only this pattern is visible, however, when the image is looked at through a red filter, the red parts of the image disappear, and the message can be easily seen.

Activity 1

See if you can find the secret message in the interactive activity below, and make sure you note it down, you will need this later.


Move your mouse across the red-reveal image below to reveal the secret message concealed within it. You can also try looking at the screen through red cellophane or something similar to achieve the same effect.

Strengths & Weaknesses


  • Hiding a message in plain sight is one of the best ways to avoid suspicion entirely
  • Messages can be hidden in pictures, text or even computer files
  • Text, symbols or even pictures can be hidden using this method


  • A form of concealment rather than encryption. If the message is spotted, it can be easily understood
  • Distinctive red pattern makes them easy to spot
  • May require special materials or equipment to create the source image/text