from Crypto.Cipher import AES
from Crypto.Util.Padding import pad
from Crypto.Random import get_random_bytes


# Generate new secret key
with open('key', 'wb') as f:
    f.write(get_random_bytes(16))

plaintext = input("Please input the message: ")

# Pad plaintext
plaintext = plaintext.encode()

plaintext = pad(plaintext, 16)

# Read Key
with open('key', 'rb') as f:
    aes_key = f.read()

# Encrypt and send (write) message
cipher = AES.new(aes_key, AES.MODE_CBC)

ciphertext = cipher.encrypt(plaintext)

with open('ctext', 'wb') as f:
    f.write(ciphertext)