sender.py

# sender.py
import socket
import os
from cryptography.hazmat.primitives import serialization, hashes
from cryptography.hazmat.primitives.asymmetric import padding
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
import pickle
# Load recipient's public key
with open("public_key.pem", "rb") as f:
    public_key = serialization.load_pem_public_key(f.read())

# Message to send
message = b"Hello from the secure sender! This is confidential."

# 1. Generate random AES key and IV
aes_key = os.urandom(32) # AES-256
iv = os.urandom(16)

# 2. Encrypt message with AES (CFB mode)
cipher = Cipher(algorithms.AES(aes_key), modes.CFB(iv))
encryptor = cipher.encryptor()
encrypted_message = encryptor.update(message) + encryptor.finalize()

# 3. Encrypt AES key with RSA (recipient's public key)
encrypted_key = public_key.encrypt(
    aes_key,
    padding.OAEP(
    mgf=padding.MGF1(algorithm=hashes.SHA256()),
    algorithm=hashes.SHA256(),
    label=None
    )
)

# 4. Package: (encrypted_key, iv, encrypted_message)
payload = pickle.dumps((encrypted_key, iv, encrypted_message))

# 5. Send via socket
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.connect(("localhost", 65432))
    s.sendall(payload)
    print("✅ Encrypted message sent!")