The Science Behind It, Codes & Ciphers

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The Science of Codes and Ciphers The Science Behind it . What is the difference between a code and a cipher? A code affects the word, and a cipher affects the individual letters. Definitions Cipher — A cipher is a system to make a word or message secret by changing or rearranging the letters in the message. Example: For example: A=G or A=&. Code — A code is a system of changing entire words or phrases into something else. Codes are not just secret messages, they can be any symbol or signal used to represent, or communicate, something else. Example: President = Eagle or Tank = 4036 Cryptology — Cryptology is the art and science of making and breaking codes. Codebreaker — A codebreaker is a person who solves secret codes and ciphers without the ‘key’. Codemaker — A codemaker is a person who makes new secret codes and ciphers. How do you break a cipher? Breaking a cipher without having the ‘key’ is difficult. The main tool is the use of a frequency list. Some letters are used more frequently than others in words. The letter used most often is “E” and the least common letter is “Z”. The order of letter frequency is: ETAOINSRHDLUCMFYWGPBVKXQJZ. Replace the frequently used letters in the cipher with the most commonly used letters. Using the frequency list will help to solve the puzzle, then the rest of the letters will need to be tried in different combinations until the message makes sense. The introduction of computers has made it more difficult to break a cipher. Materials Þ Cipher disk (1 per youth) Þ Metal fastener (1 per youth) Þ 3 x 5 cards (1 per youth to write their name in code) Þ Scissors (to share) Þ Pens/Pencils (to share) Sources Þ The Exploratorium: www.exploratorium.edu/ronh/secret/secret.html Þ The National Security Agency CryptoKids: www.nsa.gov/kids/home_html.shtml Þ Cornell University: www.math.cornell.edu/~mec/2003-2004/cryptography/subs/frequencies.html www.ext.vt.edu/topics/4h-youth/makers __________________________________________________________________________________________ .

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9 Purple 18/2
THE CONCORD REVIEW 223 A VERY PURPLE-XING CODE Michael Cohen Groups cannot work together without communication between them. In wartime, it is critical that correspondence between the groups, or nations in the case of World War II, be concealed from the eyes of the enemy. This necessity leads nations to develop codes to hide their messages’ meanings from unwanted recipients. Among the many codes used in World War II, none has achieved a higher level of fame than Japan’s Purple code, or rather the code that Japan’s Purple machine produced. The breaking of this code helped the Allied forces to defeat their enemies in World War II in the Pacific by providing them with critical information. The code was more intricate than any other coding system invented before modern computers. Using codebreaking strategy from previous war codes, the U.S. was able to crack the Purple code. Unfortunately, the U.S. could not use its newfound knowl- edge to prevent the attack at Pearl Harbor. It took a Herculean feat of American intellect to break Purple. It was dramatically intro- duced to Congress in the Congressional hearing into the Pearl Harbor disaster.1 In the ensuing years, it was discovered that the deciphering of the Purple Code affected the course of the Pacific war in more ways than one. For instance, it turned out that before the Americans had dropped nuclear bombs on Japan, Purple Michael Cohen is a Senior at the Commonwealth School in Boston, Massachusetts, where he wrote this paper for Tom Harsanyi’s United States History course in the 2006/2007 academic year.
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