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. Wax tablets were in common use then as reusable writing surfaces, sometimes used for shorthand. In his work Polygraphiae, Johannes Trithemius developed his so-called "Ave-Maria-Cipher" that can hide information in a Latin praise of God. "Auctor Sapientissimus Conseruans Angelica Deferat Nobis Charitas Potentissimi Creatoris" for example contains the concealed word VICIPEDIA. Techniques Physical Steganography has been widely used for centuries. Some examples include: Hidden messages on a paper written in secret inks. Hidden messages distributed, according to a certain rule or key, as smaller parts (e.g. words or letters) among other words of a less suspicious cover text. This particular form of steganography is called a null cipher. Messages written in Morse code on yarn and then knitted into a piece of clothing worn by a courier. Messages written on envelopes in the area covered by postage stamps. In the early days of the printing press, it was common to mix different typefaces on a printed page because the printer did not have enough copies of some letters in one typeface. Thus, a message could be hidden by using two or more different typefaces, such as normal or italic. During and after World War II, espionage agents used photographically-produced microdots to send information back and forth. Microdots were typically minute (less than the size of the period produced by a typewriter). 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. Alternative techniques included inserting microdots into slits cut into the edge of postcards. During World War II, Velvalee Dickinson, a spy for Japan in New York City, sent information to accommodation addresses in neutral South America. She was a dealer in dolls, and her letters discussed the quantity and type of doll to ship. The stegotext was the doll orders, and the concealed "plaintext" was itself encoded and gave information about ship movements, etc. Her case became somewhat famous and she became known as the Doll Woman. During World War II, photosensitive glass was declared secret, and used for transmitting information to Allied armies. Jeremiah Denton repeatedly blinked his eyes in Morse