Presentation by CDT Ashcraft

 Following WWII, tensions between the USSR and the United States necessitated a way to both launch and defend against nuclear attacks from Intercontinental Ballistic Missiles (ICBM)
 An important defense: the semiautomatic ground environment, automated system of 100 long-distance radars that transmitted tracking data, fed into primary warning center in Colorado. Machine to machine communication allowed operators to make split-second decisions using information transmitted and processed automatically by computers.
 Computer Networking, Finances, Education.
 Internet grows, problem emerges.

 Required sharing a secret number, known as the “Key”
 Symmetric key crypto lets two parties share secret messages as long as they already have a shared key
 How can two people who have never met agree on a secret shared key without a third party, who is listening, also obtaining a copy???
 Scenario: Alice and Bob are communicating on an unsecured network.

 Eve is an attacker who can see Alice and Bob’s messages
 She cannot modify them
 She is a Passive attacker
 Examples:
 Unencrypted wifi users
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Government
Internet provider
Someone else on the same network
Alice and Bob need a way to encrypt messages, but how do they choose?

 We need a numerical procedure that is easy in one direction and difficult in the opposite direction
 mod p
 Clock Arithmetic
 Pick a prime modulus such as 17
 Use a prime root of 17, such as 3
 3^x mod 17 = [0,16] equally likely
 Reverse procedure is difficult to find
 Discrete Logarithm

 To solve, it is easy with small numbers, but with big number it becomes impractical
 Using a prime modulus hundreds on digits long, it could take thousands of years to solve using computers
 The strength of a One Way Function is based on the time needed to reverse it.

 Bob and Alice each come to a solution that is not known to Eve, an eavesdropping attacker