The Secret World of Codes and Codebreaking

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The enigma project
The Secret World of Codes and Codebreaking
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Code whole words or phases are replaced by a
letter or number Cipher individual letters are
replaced with other letters or symbols
Plaintext normal English Ciphertext coded
English
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ACTIVITY 1
Decipher the ciphertext on the strip of paper.
CLUE You will have to use a pencil. But you
dont use the pencil in the usual way!
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Scytale Used by the Spartans in Ancient Greece
2500 years ago
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Scytales must be the same size to be able to
decipher a message
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Scytales must be the same size to be able to
decipher a message
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Cipher Algorithm
Key  
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(No Transcript)
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Caesar Shift Cipher
MISS ELLIS
NJTT FMMJT
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Caesar Shift Cipher
MXOLXV FDHVDU WKH URPDQ JHHCHU VTXDVKHG KLV
ZLIH LQ D OHPRQ VTXHHCHU
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ACTIVITY 2
Decipher this message. Each plaintext letter has
been moved three places forward in the alphabet
MXOLXV FDHVDU WKH URPDQ JHHCHU VTXDVKHG KLV
ZLIH LQ D OHPRQ VTXHHCHU
7K H P J
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Caesar Shift Cipher
Julius Caesar the
Roman Geezer
Squashed his wife in
A Lemon Squeezer!
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Caesar Shift Cipher
How many possible keys are there with the Caesar
Shift Cipher?
25
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ACTIVITY 3
How many possible keys are there when you swap
each letter of the alphabet with another letter?
400 million billion billion
400 000 000 000 000 000 000 000 000
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400 million billion billion keys
6.5 billion people in the world
31 million seconds in a year
If everyone in the world checked one key per
second, it would still take 2 billion years to
check them all
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Mary Queen of Scots and the Babington Plot
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One of the messages Mary Queen of Scots sent to
Babington
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ACTIVITY 4
How would you go about trying to crack this type
of cipher when there are a possible 400 million
billion billion keys?
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An unusual message
Today, by radio, and also on giant hoardings, a
rabbi, an admiral notorious for his links to
masonry, a trio of cardinals and a trio, too, of
politicians inform us all of how our country now
risks dying of starvation.
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ACTIVITY 5
Have a conversation with the person sitting next
to you WITHOUT using any words that contain the
letter E
START NOW
STOP!
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Al Kindis book written in 800 AD
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Code Breaking Tips
Common letters One letter words Common
words Double letters Clues
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WW2 Enigma Machine
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General Guderians Command-post vehicle
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(No Transcript)
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(No Transcript)
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Bletchley Park Government Code and Cipher School