Her case became somewhat famous and she became known as the Doll Woman. The stegotext was the doll orders, and the concealed "plaintext" was itself encoded and gave information about ship movements, etc. She was a dealer in dolls, and her letters discussed the quantity and type of doll to ship. During World War II, Velvalee Dickinson, a spy for Japan in New York City, sent information to accommodation addresses in neutral South America.Alternative techniques included inserting microdots into slits cut into the edge of postcards. World War II microdots were embedded in the paper and covered with an adhesive, such as collodion that was reflective and so was detectable by viewing against glancing light. Microdots were typically minute (less than the size of the period produced by a typewriter). Techniques Ī microdot cameraDuring and after World War II, espionage agents used photographically-produced microdots to send information back and forth. " Auctor Sapientissimus Conseruans Angelica Deferat Nobis Charitas Potentissimi Creatoris" for example contains the concealed word VICIPEDIA.
In his work Polygraphiae, Johannes Trithemius developed his so-called " Ave-Maria-Cipher" that can hide information in a Latin praise of God. Wax tablets were in common use then as reusable writing surfaces, sometimes used for shorthand. Histiaeus sent a message to his vassal, Aristagoras, by shaving the head of his most trusted servant, "marking" the message onto his scalp, then sending him on his way once his hair had regrown, with the instruction, "When thou art come to Miletus, bid Aristagoras shave thy head, and look thereon." Additionally, Demaratus sent a warning about a forthcoming attack to Greece by writing it directly on the wooden backing of a wax tablet before applying its beeswax surface. The first recorded uses of steganography can be traced back to 440 BC in Greece, when Herodotus mentions two examples in his Histories. The change is so subtle that someone who is not specifically looking for it is unlikely to notice the change.Ī chart from Johannes Trithemius's Steganographia copied by Dr John Dee in 1591 For example, a sender might start with an innocuous image file and adjust the color of every hundredth pixel to correspond to a letter in the alphabet. Media files are ideal for steganographic transmission because of their large size. In digital steganography, electronic communications may include steganographic coding inside of a transport layer, such as a document file, image file, program, or protocol. Steganography includes the concealment of information within computer files. Whereas cryptography is the practice of protecting the contents of a message alone, steganography is concerned with concealing the fact that a secret message is being sent and its contents. Plainly visible encrypted messages, no matter how unbreakable they are, arouse interest and may in themselves be incriminating in countries in which encryption is illegal. The advantage of steganography over cryptography alone is that the intended secret message does not attract attention to itself as an object of scrutiny. Some implementations of steganography that lack a shared secret are forms of security through obscurity, and key-dependent steganographic schemes adhere to Kerckhoffs's principle. For example, the hidden message may be in invisible ink between the visible lines of a private letter. Generally, the hidden messages appear to be (or to be part of) something else: images, articles, shopping lists, or some other cover text. The first recorded use of the term was in 1499 by Johannes Trithemius in his Steganographia, a treatise on cryptography and steganography, disguised as a book on magic. The word steganography comes from Greek steganographia, which combines the words steganós ( στεγανός), meaning "covered or concealed", and -graphia ( γραφή) meaning "writing". In computing/electronic contexts, a computer file, message, image, or video is concealed within another file, message, image, or video. Steganography ( / ˌ s t ɛ ɡ ə ˈ n ɒ ɡ r ə f i/ ( listen) STEG-ə- NOG-rə-fee) is the practice of concealing a message within another message or a physical object. The same image viewed by white, blue, green, and red lights reveals different hidden numbers.
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