Secret Codes

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Secret Codes
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• A code is a system of symbols, letters, words, or
  signals that are used instead of ordinary words
  and numbers to send messages or store
  information. A code is used to keep the message
  short or to keep it secret.
•  
• Codes and ciphers are forms of secret
  communication. A code replaces words, phrases, or
  sentences with groups of letters or numbers,
  while a cipher rearranges letters or uses
  substitutes to disguise the message. This process
  is called encryption or enciphering. The science
  that studies such secret communication is called
  cryptology.

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• Secret writing has been employed about as long as
  writing has existed. Codes have been used
  throughout history whenever people wanted to keep
  messages private. Cryptology has long been
  employed by governments, military, businesses,
  and organizations to protect their messages.
  Today, encryption is used to protect storage of
  data and transactions between computers.

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Pig Pen Code

• Scytale Messages/Cylinder Writing

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Lovells Cipher

• Lovell's cipher, advocated by James Lovell of the
  Committee of Foreign Affairs, is one of many
  codes and ciphers used during the American
  Revolutionary War.
• The following example shows a cipher table for a
  keyword "CR". This is the keyword assigned to
  John Adams.

• 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
  16 17 18 19 20 21 22
• C D E F G H I J K L M N O P
  Q R S T U V W X
• R S T U V W X Y Z A B C D
  E F G H I J K L
• 24 25 26 27
• Y Z A B
• M N O P Q

What does this message say? SMEQ DEFPQZED MCQ
OX!
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Navajo Code Talkers in WWII

• Code talkers were United States soldiers during
  the world wars who used their knowledge of
  Native-American languages as a basis to transmit
  coded messages. In particular there were
  approximately 400-500 Native Americans in the
  United States Marine Corps whose primary job was
  the transmission of secret tactical messages.
  Code talkers transmitted these messages over
  military telephone or radio communications nets
  using formal or informally developed codes built
  upon their native languages. Their service
  improved communications in terms of speed of
  encryption at both ends in front line operations
  during World War II.

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Enigma in WWI

• Enigma was invented by German engineer Arthur
  Scherbius at the end of World War I. The early
  models were used commercially from the early
  1920s, and adopted by military and government
  services of several countries most notably by
  Nazi Germany before and during World War II.

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Other Examples of Codes

• American Sign Language
• Mirror Writing
• Morse Code
• Binary Code
• Passwords
• Combination Locks

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Resources

• http//www.cerias.purdue.edu/education/k-12/teachi
  ng_resources/lessons_presentations/cryptology.html
  
• http//www.nsa.gov/programs/kids/standard/lab/elem
  entary/index.shtml