Cryptology

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Cryptology

• Terminology and Early History

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Cryptology Terms

• Cryptology
• The science of concealing the meaning of messages
  and the discovery of the meaning of hidden
  messages
• Plaintext
• A message in ordinary language
• Codetext or ciphertext
• The plain text message transformed using a code
  or cipher so that it cannot be read without
  knowing the code or cipher

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Cryptology Terms

• Cryptography
• The study of how to conceal the meaning of
  messages (encryption) using codes and ciphers.
• Sometimes more generally used as a synonym for
  Cryptology
• Cryptanalysis
• The study of how to discover the meaning of
  hidden messages (decryption)

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Cryptology Terms

• Code
• A system for altering a text by substituting
  different words or symbols for words or phrases
  in the plaintext
• Cipher
• A system for altering a text by substituting
  different symbols for the plaintext symbols
  (letters), for example by substituting different
  letters for the plaintext letters according to
  some system.

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Cryptology Terms

• Steganography
• The science of hiding the existence of a message
  (rather than changing the form of the message so
  that it cannot be read)

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Highlights in the History of Cryptology

• Timeline of Cryptology

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How would you hide a message?
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How would you hide a message?

• Transposition
• Substitution
• Cipher, substituting for each letter
• Code, substituting for words or phrases

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Cryptanalysis

• How do your break a code so you can read it?
• Example Sherlock Holmes problem of the Dancing
  Men.

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