The code for a secure Block Cipher Encryption in Python

BlockCipher.py

def chunk_message(message, block_data=4):
    message_chunked = []
    block = 0
    block_count = len(message) // block_data + 1
    for character in range(block_count * block_data):
        block = block << 8

        if character < len(message):
            block += ord(message[character])
        else:
            block += 0

        if block.bit_length() > (block_data - 1) * 8:
            message_chunked.append(block)
            block = 0
    return message_chunked


def apply_shift(message_chunked, key, block_data=4):
    encrypted_message = []
    max_bit = block_data * 8
    for n in range(len(message_chunked)):
        block = message_chunked[n]
        carry = block % (2**key)
        carry = carry << (max_bit - key)
        encrypted_character = (block >> key) + carry
        encrypted_message.append(encrypted_character)
    return encrypted_message


def string_message(message_chunked, block_data = 4):
    message = ""
    for i in range(len(message_chunked)):
        block = message_chunked[i]
        for x in range(block_data):
            byte = (block >> (8 * (block_data - 1 - x))) % 2**8
            message += chr(byte)
    return message


unencrypted_text = "Hello World!"
key = 7
block_list = chunk_message(unencrypted_text)
encrypted_list = apply_shift(block_list, key)
encrypted_string = string_message(encrypted_list)
print(encrypted_string)