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In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code, or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet .
Secret Service code name. President John F. Kennedy, codename "Lancer" with First Lady Jacqueline Kennedy, codename "Lace". The United States Secret Service uses code names for U.S. presidents, first ladies, and other prominent persons and locations. [1] The use of such names was originally for security purposes and dates to a time when ...
Book cipher. The King James Bible, a highly available publication suitable for the book cipher. A book cipher is a cipher in which each word or letter in the plaintext of a message is replaced by some code that locates it in another text, the key . A simple version of such a cipher would use a specific book as the key, and would replace each ...
Top Secret is the highest level of classification. However some information is further categorized/marked by adding a code word so that only those who have been cleared for each code word can see it. A document marked SECRET (CODE WORD) could be viewed only by a person with a secret or top secret clearance and that specific code word clearance.
The pigpen cipher (alternatively referred to as the masonic cipher, Freemason's cipher, Rosicrucian cipher, Napoleon cipher, and tic-tac-toe cipher) [2] [3] is a geometric simple substitution cipher, which exchanges letters for symbols which are fragments of a grid. The example key shows one way the letters can be assigned to the grid.
A list of several such code words can be seen at Byeman Control System. Exercise terms – a combination of two words, normally unclassified, used exclusively to designate an exercise or test; In 1975, the Joint Chiefs of Staff introduced the Code Word, Nickname, and Exercise Term System (NICKA) which automated the assignment of names. NICKA ...
Code wheel. A code wheel is a type of copy protection used on older computer games, often those published in the late 1980s and early 1990s. It evolved from the original "manual protection" system in which the program would require the user to enter a specific word from the manual before the game would start up or continue beyond a certain point.
However, in cryptography, code has a more specific meaning: the replacement of a unit of plaintext (i.e., a meaningful word or phrase) with a code word (for example, "wallaby" replaces "attack at dawn"). A cypher, in contrast, is a scheme for changing or substituting an element below such a level (a letter, a syllable, or a pair of letters, etc ...