diffie_hellman_key_exchange.py

#!/usr/bin/env python2

# https://www.youtube.com/watch?v=YEBfamv-_do

from random import randrange

public_prime = 67280421310721       # aka p
public_base = 3                     # aka g

def generate_key():
    return randrange(123, 456) % public_prime

alice_private_key = generate_key()
bob_private_key = generate_key()
print 'private keys', alice_private_key, bob_private_key

alice_public_key = public_base ** alice_private_key
bob_public_key = public_base ** bob_private_key

alice_common_private_key = (bob_public_key ** alice_private_key) % public_prime
bob_common_private_key = (alice_public_key ** bob_private_key) % public_prime

assert alice_common_private_key == bob_common_private_key
print 'common private key', alice_common_private_key, bob_common_private_key