How Deffie-Hellman Exchanges work
Diffie-Hellman authentication was invented in 1976 by Whitfield Diffie and Martin
Hellman. It has become one of the most commonly used public key exchanges used
today. Below is an example of how Deffie-Hellman key exchanges work.
Diffie-Hellman exchange = (magic math to calculate a secure secret value)
HOW CALCULATED:
P – large prime
G – number smaller than “P”
EXAMPLE =
P = 1021 – NOT SECRET part of RFC
G = 37 – NOT SECRET part of RFC
Each peer comes up with secret number (RANDOM) =
22 – first group
123 – second group
Have students open windows calculator in scientific mode
Formual = “G (X^Y) private value [mod] P =”
Group A = 37 (X^Y) 22 [mod] 1021 = 399
Group B = 37 (X^Y) 123 [mod] 1021 = 170
Then reverse in following way:
Received value (X^Y) private value (MOD) P
Group B = 399 (X^Y) 123 (MOD) 1021 = 213
Group A = 170 (X^Y) 22 (MOD) 1021 = 213
399 and 170 is shared public key
213 shared secret key