Title: The History of Cryptography
1The History of Cryptography
2- Cryptography
- Cryptanalysis
- Codes
- Ciphers
- Keys
3The 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
4The 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.
5The 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.
6 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
7World 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.
8World 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.
9World 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. -
10Public 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.
11How 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.
12The 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.
13The End