Editing Public Key Crypto (section)

== <span style="color: #FFFFFF;">Applying</span> ==
'''Modeling 'The Diffie-Hellman Key Exchange':'''
<syntaxhighlight lang="python">
def generate_shared_secret(g, p, my_private_key, their_public_part):
    """
    Shows how two people can create a secret key 
    without ever sending the key itself.
    Formula: (g^b mod p)^a mod p == (g^a mod p)^b mod p
    """
    shared_secret = (their_public_part ** my_private_key) % p
    return shared_secret

# Alice and Bob agree on g=5, p=23
# Alice chooses private_a=6. Bob chooses private_b=15.
# Alice sends (5^6 mod 23) = 8. Bob sends (5^15 mod 23) = 19.

alice_secret = generate_shared_secret(5, 23, 6, 19)
bob_secret   = generate_shared_secret(5, 23, 15, 8)

print(f"Alice's secret: {alice_secret}")
print(f"Bob's secret:   {bob_secret}")
# They both calculated '2' without ever sending it!
</syntaxhighlight>

; Asymmetric Landmarks
: '''PGP (Pretty Good Privacy)''' → The first software to bring public-key encryption to the masses for email.
: '''Bitcoin''' → Uses '''ECC''' to prove ownership of coins without needing a bank.
: '''The Green Padlock''' → The visual indicator in your browser that a site is using public-key crypto (TLS).
: '''SSH Keys''' → Used by developers to log into servers without using a password.
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