The History of Cryptography

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The History of Cryptography

• From 500 B.C.

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• Cryptography
• Cryptanalysis
• Codes
• Ciphers
• Keys

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The Early Breakthroughs

• Ancient Greeks - shaved the head of slaves
• - used a transposition
  cipher by wrapping leather round a
  scytale.

• An early form of a substitution cipher appears in
  a text based on manuscripts from the 4th Century
  B.C.

• The Kama Sutra! women should study
  mlecchita-vikapla.

• Julius Caesar also used cryptography he
  invented the Caesar shift cipher

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The Arab Cryptanalysists

• Cryptographers were winning!
  
  - Caesar shift cipher has only 26 permutations
  
  - but random substitution has 26!

• This began to change around 750 A.D. where in the
  Islamic world were monoalphabetic ciphers were
  already in use.

• Religious scholars were analysing the texts of
  the Prophet Muhammad and discovered that some
  letters occurred more frequently than others!
  This led to the discovery of frequency analysis
  to solve monoalphabetic ciphers.

• Im sure you all know the letter E is most
  prevalent in the English language its frequency
  is 12.7.

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The Europeans

• The Europeans were far behind. Monks were the
  only people who studied cryptanalysis and slowly
  they reintroduced it to the Western world.
• By the 15th century, about 700 years after the
  Arabs, frequency analysis is discovered.
• Mathematically speaking, a breakthrough was
  needed for cryptography. They have added null
  letters, enciphered spaces and misspelled words
  to distort frequency, but it is essentially the
  same.
• This breakthrough came from several men, but the
  credit was given to Blaise de Vigenere. He
  introduced a polyalphabetic cipher, published in
  1586 and unbroken until the late 19th century.

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A B C D E F G H I J K L M N O P Q R S T U
V W X Y Z A A B C D E F G H I J K L M N O P Q R
S T U V W X Y Z B B C D E F G H I J K L M N O P
Q R S T U V W X Y Z A C C D E F G H I J K L M N
O P Q R S T U V W X Y Z A B D D E F G H I J K L
M N O P Q R S T U V W X Y Z A B C E E F G H I J
K L M N O P Q R S T U V W X Y Z A B C D F F G H
I J K L M N O P Q R S T U V W X Y Z A B C D E G
G H I J K L M N O P Q R S T U V W X Y Z A B C D E
F H H I J K L M N O P Q R S T U V W X Y Z A B C
D E F G I I J K L M N O P Q R S T U V W X Y Z A
B C D E F G H J J K L M N O P Q R S T U V W X Y
Z A B C D E F G H I K K L M N O P Q R S T U V W
X Y Z A B C D E F G H I J L L M N O P Q R S T U
V W X Y Z A B C D E F G H I J K M M N O P Q R S
T U V W X Y Z A B C D E F G H I J K L N N O P Q
R S T U V W X Y Z A B C D E F G H I J K L M O O
P Q R S T U V W X Y Z A B C D E F G H I J K L M N
P P Q R S T U V W X Y Z A B C D E F G H I J K L
M N O Q Q R S T U V W X Y Z A B C D E F G H I J
K L M N O P R R S T U V W X Y Z A B C D E F G H
I J K L M N O P Q S S T U V W X Y Z A B C D E F
G H I J K L M N O P Q R T T U V W X Y Z A B C D
E F G H I J K L M N O P Q R S U U V W X Y Z A B
C D E F G H I J K L M N O P Q R S T V V W X Y Z
A B C D E F G H I J K L M N O P Q R S T U W W X
Y Z A B C D E F G H I J K L M N O P Q R S T U V
X X Y Z A B C D E F G H I J K L M N O P Q R S T U
V W Y Y Z A B C D E F G H I J K L M N O P Q R S
T U V W X Z Z A B C D E F G H I J K L M N O P Q
R S T U V W X Y
Vigenere Cipher
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World War I

• Due to the invention of the radio, allied
  forces were intercepting hundreds of messages a
  day.

• Arthur Zimmerman, the German foreign minister was
  hoping to keep the U.S.A. out of the war.
• His telegram was intercepted and passed to Room
  40.
• This persuaded the Americans into the war.
• Room 40 were criticised in a cover up story.

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World War II

• The Enigma is probably the best known cipher of
  all.
• The Germans believed it unbreakable, it was a
  machine of rotating wheels, electrical contacts
  and wires that could be swapped giving rise to
  10,000,000,000,000,000 keys.
• Poland however felt they could be threatened by
  Germany or Russia.
• The Germans, however increased the choice of
  wheels, so increasing the number of keys that
  could be used.

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World War II and Bletchley Park

• Poland did not have the capacity to cope with
  Enigma any more.
• Room 40 moved to Bletchley Park and became home
  to over 1000 staff working on decrypting German
  messages as the war began.
• Here Alan Turing became famous for the work he
  did on the Enigma, carrying on Rejewskis work to
  gain valuable information for the Allies.
• Also, a world first, an a programmable computer
  named Colossus was built to break Lorenz, a
  cipher used personally by Hitler. Another
  secret only revealed years later.

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Public Key Cryptography

• After the war cryptography began making its way
  into everyday life, as did computers. Gradually a
  problem arose.
• How to distribute keys safely?
• The idea was thought of by Diffie, Hellman and
  Merkle in 1976. They came up with the idea of
  needing a public key so a message can be
  encrypted, and a private key so that you can
  decrypt the message using an asymmetric cipher.
• In the end it was a different team who solved it
  Rivest Shamir and Adleman who came up with RSA.

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How does it work?

• Well you should all be able to remember
  
• Core A anyone?
• Winnie the pooh picks two, very large prime
  numbers, p and q.
• p x q N
• He also picks another number e. Together these
  numbers are his public key.
• Then a message that Piglet wants to send is put
  into binary and this number M is encrypted
  according to C Me (mod N) and C is sent to
  Winnie the pooh.
• This is impossible to work out without the
  private key as long as the primes used for p and
  q are big enough.
• The private key is d, worked out from p and q
  using Euclids algorithm.

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The rest.

• It was recently discovered, much like the first
  programmable computer, that actually GCHQ first
  found RSA, four years earlier, but kept it
  secret.
• RSA is responsible for protecting most
  communications and is widely used as there is
  still no shortcut to factoring a large number.
• There is an ongoing debate about whether strong
  encryption should be available to everyone for
  personal privacy or if it shouldnt - so law
  enforcement can still get information from
  criminals.

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The End