Steganography is the practice of hiding a secret message inside another message or a physical object that isn’t secret. Think Tim Messenger, Adam Buxton’s character in the film ‘Hot Fuzz’ (one of my all-time favourites) who hides messages in misspelt newspaper headlines about what’s going on in the village of Sandford (‘He’s Judge Judy and executioner!’). Other examples of steganography include invisible ink or playing a record backwards to reveal a hidden message.
Steganography is action – if you look at the first image under white, blue, green and red lights you see different hidden numbers (not that well-hidden, but still).
Etymology time (my favourite time). ‘Steganography’ comes from the Greek word steganographia. That’s made up of steganós, meaning ‘covered or concealed’, and ‘-graphia’ meaning ‘writing’. The first recorded use of the term was in 1499 by one Johannes Trithemius (amazing name) who wrote a book called ‘Steganographia’. It was a treatise on cryptography and steganography disguised as a book on magic.
The advantage of steganography over cryptography – i.e. converting text into something unintelligible so only someone who has the key or cipher can convert it back – is that the secret message doesn’t attract attention because it’s hidden in something else. So while cryptography is just about protecting the contents of a secret message, steganography hides the fact that there’s a message at all.
The earliest recorded use of steganography was in 440 BC in Greece, which Herodotus (writer, philosopher and all-round clever dude) mentions in his book ‘Histories’ (an account of the Greco-Persian Wars). A ruler by the name of Histiaeus sent a message to a minion about an upcoming revolt by shaving the head of a servant, tattoing the message on to his scalp, then sending him to deliver it once his hair had regrown. Obviously there are a lot of issues here, not least that hair growth takes a long time. Oh, and you need a new servant for every message.
Today steganography has moved on a bit. The word is commonly used to descibe the ways hackers infect people’s computers i.e. by hiding nasty bits of code in common-or-garden documents like PDFs. Then when you open the doc it installs a horrible bit of malware or ransomware on your PC. Bastards.
Warning: contains a lot of blood and some swearing (just a ‘wanker’).