Steganography is the act of hiding a message within another message or image.
Steganography has roots in Greek with steganos, which means protected, or covered, and graphei which means writing.
The first allusion to steganography can be tracked to Herodotus in 440 BCE. He writes about two examples of steganography in his book, Histories. After that, Demaratus, king of Sparta, sent a warning to Greece using a wooden tablet and beeswax to hide the message. The message contained news of a plotted attack against Greece. The first usage of the word steganography was in 1499 by Johannes Trithemius, who wrote Steganographia. Steganographia was an exposition of steganography, under the guise of a book about magic.
Ways in which steganography is used
-Hidden messages via messengers: carried by messengers using either wax tablets, or literally written on the messenger himself, ancient Grecians used to send each other secrets about invasions, war tactics and the like using steganography.
-Hidden messages via printed text: after the printing press was invented, many printers mixed typefaces due to lack of a certain character. However, some printers would use the other characters (often times the characters in italics) to spell out secret messages on a particular page.
-Hidden messages via invisible or secret ink: the French began using invisible ink during World War II; other messages contained secret inks, using substances that would become visible by heating the paper.
-Hidden messages via the blinking of the eye: one of the most historically famous cases of steganography is when Jeremiah Denton, a prisoner of war held captive by the North Vietnamese, blinked “t-o-r-t-u-r-e” during a 1966 press conference. Everyone watching television was able to see him blinking, though it took a trained eye to decode the blinks. He used Morse code to send a message to those that could help him.
-Hidden messages via images: occurring digitally, some people are able to manipulate the bits of an image in order to encode a secret message.
The positive aspect to using steganography, as opposed to cryptology, is as follows:
When using cryptology, the secret “code” is very apparent, and one can “crack” the code (or attempt to crack the code). However, steganography typically remains hidden; to the untrained or non-searching eye, nothing seems amiss.