Challenge 5: Implement Diffie-Hellman Key Exchange

Level: Intermediate

Description: Simulate the Diffie-Hellman key exchange algorithm to securely share a symmetric key between two parties.

Challenge Text:

Given prime p = 23, base g = 5
Party A's private key: 6
Party B's private key: 15

Instructions: 1. Compute Party A's and Party B's public keys. 2. Compute the shared secret key for both parties. 3. Validate that both parties have the same shared secret key.

Answer: Shared secret key: 2

Code:

p = 23
g = 5
a_private = 6
b_private = 15

# Compute public keys
A_public = (g ** a_private) % p
B_public = (g ** b_private) % p

# Compute shared secret key
shared_secret_A = (B_public ** a_private) % p
shared_secret_B = (A_public ** b_private) % p

print("Shared secret key (Party A):", shared_secret_A)
print("Shared secret key (Party B):", shared_secret_B)