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Fundamentals of Cryptography
Chapter 2

Presentation slide for courses, classes, lectures et al.
1

History of Cryptography
Oldest example
Hieroglyphics

Hieroglyphics (cont)

Hieroglyphics (cont)

Scytale
Popular with Spartans
Example of what is known as Transposition Cipher

Caesar Cipher
Example of a Substitution Cipher
Vulnerable to frequency analysis
ETANORISH

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Caesar Cipher Example
Caesar Cipher

Polyalphabetic Cyphers
In 1452 Lean Battista Alberti created the polyalphabetic substitution cypher.
Alberti is known as the father of Western cryptography
Polyalphabetic substitution makes cryptanalysis harder because multiple alphabets are used in the process.
Vigenere cypher is a much more complex form of Alberti’s cypher.
Vigenere used 26 alphabets (Alberti used 2)
Go to http://cs.widener.edu/~
chiffens/Eexplained.html to see an example of how it works.

American Civil War
Telegraph created need for increased encryption
Complex substitutions and transposition ciphers
Flag signals
Ulysess S Grant attributed many Union victories to the intelligence gained from codebreaking

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Modern Examples (1900+)
Enigma
Ultra
Purple Code

Enigma
Used by World War II Germany
Special version for Wehrmacht and Kriegsmarine
Japanese created own version

Enigma Example

Enigma Rotors

Ultra vs. Enigma
Ultra: Allied forces initiative to overcome the Germany Enigma code
Based in Bletchley Park in the UK
Worked on by 9000 people
Notably worked on by Alan Turing
Referenced in film “The Imitation Game”

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Japanese Purple (JN-25)
Variant of Enigma
Did not use rotors
Broken by US “Magic” program prior to the start of US entry into WW2
Intelligence gathered gave huge advantage to America during the Battle of Midway

Purple Machine Example

1970s
Data Encryption Standard (DES)
RSA Algorithm