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Alice.py
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Alice.py
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import socket
import binascii, os
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import padding, hmac, hashes
def encrypt_message(message, shared_key, iv):
cipher = Cipher(algorithms.AES(shared_key), modes.CBC(iv), backend=default_backend())
# Pad the message to ensure its length is a multiple of the block size
padder = padding.PKCS7(algorithms.AES.block_size).padder()
padded_message = padder.update(message.encode()) + padder.finalize()
# Encrypt the padded message
encryptor = cipher.encryptor()
ciphertext = encryptor.update(padded_message) + encryptor.finalize()
return ciphertext
def generate_hmac(message, shared_key):
h = hmac.HMAC(shared_key, hashes.SHA256(), backend=default_backend())
h.update(message.encode())
return h.finalize()
def decrypt_message(encrypted_message, shared_key, iv):
cipher = Cipher(algorithms.AES(shared_key), modes.CBC(iv), backend=default_backend())
decryptor = cipher.decryptor()
# Decrypt the ciphertext
decrypted_padded_message = decryptor.update(encrypted_message) + decryptor.finalize()
# Unpad the decrypted message
unpadder = padding.PKCS7(algorithms.AES.block_size).unpadder()
decrypted_message = unpadder.update(decrypted_padded_message) + unpadder.finalize()
return decrypted_message.decode()
def alice(shared_key):
host = 'localhost'
port = 12345
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((host, port))
print("Alice: Connected to server")
while True:
message = input("Alice: Enter the message to send to Bob (type 'exit' to quit): ")
if message == 'exit':
break
iv = os.urandom(16)
# Encrypt message
encrypted_message = encrypt_message(message, shared_key, iv)
# Generate HMAC
hmac_digest = generate_hmac(message, shared_key)
print("Alice: IV:", binascii.hexlify(iv))
print("Alice: Encrypted message:", binascii.hexlify(encrypted_message))
print("Alice: Hash:", binascii.hexlify(hmac_digest))
# Send encrypted message and HMAC to Bob
s.sendall(iv + encrypted_message + hmac_digest)
print("Alice: Encrypted message and Hash sent to Bob")
# Receive encrypted response from Bob
iv_bob = s.recv(16)
encrypted_response = s.recv(1024)
# Extract HMAC from received data
received_hmac = encrypted_response[-32:]
encrypted_response = encrypted_response[:-32]
# Generate HMAC from the decrypted message
computed_hmac = generate_hmac(decrypt_message(encrypted_response, shared_key, iv_bob), shared_key)
# Compare computed HMAC with received HMAC
if computed_hmac == received_hmac:
print("Alice: Hash verified.")
print("Alice: Decrypted response from Bob:", decrypt_message(encrypted_response, shared_key, iv_bob))
else:
print("Alice: Hash verification failed. Message integrity compromised.")
s.close()
# Take shared key from user input
shared_key_hex = input("Enter the shared key in hexadecimal format: ")
shared_key = binascii.unhexlify(shared_key_hex)
# Start Alice
alice(shared_key)