hidden text which recommends a "hit" on someone: Historically, users of concealment ciphers often used substitution and transposition ciphers on the data prior to concealment. For example, Cardinal Richelieu is said to have used a grille to write secret messages, after which the blank spaces were filled out with extraneous matter to create the impression of a continuous text. Dot null cipher A dot or pinprick null cipher is a common classical encryption method in which dot or pinprick is placed above or below certain letters in a piece of writing. An early reference to this was when Aeneas Tacticus wrote about it in his book On the Defense of Fortifications. The Germans upgraded this to a dot of invisible ink during World War I and World War II. In England pinpricks in newspapers were once a popular way to send letters with little or no cost. If you place dots far apart, it could be used well. Make sure to keep the dots small and to use something that makes sense - no advanced computer coding books between package deliverers unless both have clearly indicated that they do it or are very interested in it. You also both need to know which page, chapter, article, or section is used, and if you plan to use this as a system you should find several places. Another option is to have an indicator, such as the date in a newspaper, which shows which page the message is on. This version is less secure. Acrostics The acrostic puzzle is an extended form of null cipher, but not an Anacrostic (in which you use a set of lettered clues with numbered blanks representing the letters of the answer to figure out the second part, a long series of numbered blanks and spaces representing a message into which the answers for the clues fit). Acrostics in poems and other written works that are not referenced to are a type of Null cipher. This method is often used to secretly insult a famous or important individual. For example, Rolfe Humphries received a lifelong ban from contributing to Poetry Magazine after he wrote and tried to publish "a poem containing a concealed scurrilous phrase aimed at a well-known person", namely Nicholas Murray Butler. Definition of a null Put simply, a null cipher is any cipher which involves a number of nulls, or decoy letters. As well