from Crypto.Cipher import AES # AES crypto
from Crypto.Random import get_random_bytes
 
def add_padding(msg):
    if len(msg) % 16 != 0:
        # message length must be a factor of 16!!!
        nb_of_chars_to_pad =  16 - (len(msg) % 16)
        padded_msg = msg + (" " * nb_of_chars_to_pad)
        return padded_msg
    # message length is already a factor of 16
    return msg
 
def encrypt_message(plaintext, key, initialization_vector):
    # pad the msg if necessary
    plaintext = add_padding(plaintext)
    plaintext_bytes = plaintext.encode("utf_8")
    # create a new AES cypher. AES hasn't been broken yet, so we're safe as long as no one knows our key!
    # we use CBC mode, so we need an initialization vector.
    cipher = AES.new(key, AES.MODE_CBC, initialization_vector)
    ciphertext = cipher.encrypt(plaintext_bytes)
    return ciphertext
 
 
 
def decrypt_message(ciphertext, key, initialization_vector):
    if (len(ciphertext) % 16) != 0:
        print("Cipher has not the correct length, this was not encrypted by us.")
        #return
    cipher = AES.new(key, AES.MODE_CBC, initialization_vector)
    plaintext = cipher.decrypt(ciphertext)
    return plaintext
 
# create key and initialization vector
secret_key = b"_fl{CR-mCpaxyep}" # must be 16 bytes
secret_initialization_vector = secret_key
 
print(encrypt_message("aaaaaaaaaaaaaaaa", secret_key, secret_initialization_vector))

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