The Evolution of Secret Writing

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The Evolution of Secret Writing

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• Introduction earliest historybarrydog
• Steganography cryptographyVOYAGE
• Transpositionabchoas
• Substitutionbush

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Speaking of code

• movieMercury Rising ?Infernal affairs(MORSE
  code)
• novelSherlock Holmes
• cartoonConan
• The communication during war or between lovers
  etc.
• Maybe now you would like to know
• the evolution of secret writing

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The earliest history

• According to the father of historyHerodotus
• The conflicts between Greece and Persia
• The art of secret writing saved Greece from being
  conquered by Xerxes, king of kings, leader of
  Persians.
• This is what happened during the time of
  Xerxes, the Xerxes who ruled over 127 provinces
  stretching from India to Cush(Esther 11,From
  Bible)

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The earliest history

• Demaratus (Who wanted to notify Sparta and Athen
  Xerxes intended to invade Greece )
• 1.scraping the wax off a pair of wooden
  folding tablets
• 2.writing on the wood
• 3.covering the message over with wax again.

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Another exampleHistaiaeus

• He wanted to encourage Aristagoras of Miletus to
  revolt against the Persian king.
• Way of secret writing
• 1.shave the head of a messenger
• 2.The message on his scalp

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One day, if you are a

• CIA Agent

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First Hide your message

• steganography
• it means that use many ways to make your enemy
  can not find your message
• It is derived from Greek words steganos, meaning
  covered, and graphein, meaning to write.

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For example

• 1.The chinese wrote messages on fine silk, which
  was scrunched into a tiny ball and covered in
  wax. Then the messenger would swallow the ball of
  the wax
• Writing in the invisible ink
• for example milk, organic fruit
• because they all are rich in carbon and
  therefore char easisy.

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But

• If the message is still found by your enemy, they
  will know everything
• So we need to find other way to hide not only the
  existence of the message but its meaning

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Second hide the meaning

• Cryptography
• It means use many kind of ways to make the
  meaning of your message hidden.
• It is derived from the Greek word kryptos,
  meaning hidden

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How to

• The message is scrambled according to a
  particular protocol which is agreed beforehand
  between the sender and the intended recipient
• Thus the recipient can reverse the scrambling
  protocol and make the message comprehensible

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What Is Transposition ?

• Rearranged letters (Anagram)
• Ex. Now Eat
• Security v.s Difficult
• Random Transposition
• Tea v.s I saw my doctor this morning.
• ? There are 23! distinct arrangements.

Now ? Won, Onw, Wno Eat?Tea
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Unscrambling System(1)

• Rail fence
• THY SECRET IS THY PRISONER IF THOU LET IT GO,
  THOU ART A PRISONER TO IT
• 
  ?

T Y E R T S H P I O E T O L T T
O H U R A R S N R O T H S C E I
T Y R S N R F H U E I G T O A T P
I O E T I ?
TYERTSHPIOEITOLTTOHURARSNRQTHSCEITYRSNRFHUEIGTOATP
IOETI
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Unscrambling System(2)
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Cryptography--Substitution

• Caesar Code
• In transposition each letter retains its identity
  but changes its position, whereas in substitution
  each letter changes its identity but retains its
  position.

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• When we substitute on character for
• another to conceal the original, we are using a
  substitution cipher. The oldest is one used by
  Julius Caesar, who added 3 to each of his letter
  numbers to conceal the real message.
• For example
• Using the Caesar cipher, from "Hello", we get
• "khoor"

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Caesars Cipher with a Keyword

• Because it is difficult to remember an
  incoherent string of 26 letters, cipher alphabets
  are often based on a single word that is easy to
  memorize. The simplest method is to write out the
  keyword, omitting any repeated letters, then to
  follow it with the remaining letters of the
  alphabet in order.
• Here is a Substitution Cipher with zebra lips as
  the keyword.

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To sum up