Secret Code Hidden in Plain Sight

By Simon Batt / Secret Coding for Children / December 2021 Issue

Image by Marco Verch Professional Photographer on Flickr

Looking for a new way to encode your secret messages? Try steganography!

Secret codes can take all kinds of forms. Sometimes they’re hidden in something else, and other times they’re broadcast in broad daylight but with a strong enough encryption to prevent people from cracking it open. But sometimes you’ll stare at a code and not even realize it is one.

This is the case of steganography. It may sound like a weird dinosaur, but it’s in fact the science of hiding a code within something that looks normal. That way, you think there is no code at all, when in fact, you’re looking right at it!

The earliest example of steganography was back in 440 BC, in Greece. A smart Greek ruler called Histiaeus sent a message to his pal Aristagoras by shaving one of his slave’s head and tattooing the message onto it. The slave’s hair regrew, which hid the message from view. Then, when the slave arrived at Histiaeus’s place, he shaved off the hair again to reveal the secret message.

This gives you an idea of what steganography is. It’s a way of hiding a message in plain sight, where people ‘see’ the message but don’t realize it’s a message until it arrives at the recipient.
One common example of steganography is hiding text in pictures. We don’t mean writing the text in a tiny font on the image, or doing some tricky illusions. We mean hiding text within the data that makes up the image which someone else can extract.

The key is to make really, really tiny changes that a human can’t detect, but a computer can. For instance, an image could have a few bytes of data shifted from the original in a way where someone can sneak a message into.

The change is so slight, a human would have a very hard time detecting the difference between the original image and one with a secret message in it. Now all the code maker has to do is program a computer tool that scans the data of images with secret messages in them and shows the deciphered message on-screen so that humans can read them.

It’s not just images, though. You can hide messages in audio and video files, too. This makes steganography a prime choice for hackers, who use this tactic to hide viruses in files that otherwise look totally innocent.

So the next time you want to send a secret message, think about how you can send it in a way that everyone can see, but nobody thinks is a secret message without special knowledge. It’s a handy way to get a message across, even if everyone sees it beforehand!

Learn More

History of Steganography

https://en.wikipedia.org/wiki/Steganography#History

What is steganography? A complete guide to the ancient art of concealing messages

https://portswigger.net/daily-swig/what-is-steganography-a-complete-guide-to-the-ancient-art-of-concealing-messages

Simon Batt

Simon Batt is a UK-based tech enthusiast and all-around geek. His favourite things are cups of tea, cats, and new gadgets, even though they never mix well.

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