helper_functions.py

"""
Helper Functions 
"""
import random
import string


def get_byte_list_from(data_string):
    """
    Args: 
        data_string: a string to convert to bytes
                     length should be a multiple of 4
    Return:
        A list of lists with bytes corresponding to the data_string
    """
    return [list(bytes(data_string[i:i+4], 'utf-8')) for i in range(0,len(data_string), 4)]

def generate_random_key(key_size):
    """
    Generates a random key from uppercase characters and digits.
    Args: 
        key_size: an integer; the desired list length
    Returns:
        A list of bytes corresponding to the randomly generated key.
    """
    rand_key = bytes(random.randint(0,255) for _ in range(key_size))
    return list(rand_key)

def initialization_vector(block_size=16):
    """
    Generate an initialization vector for AES Cipher Block Chaining Mode
    See aes_test.py test_cbc_on_file function for example of use.
    block_size should be the same size as the key_size.

    Args:
        block_size: an integer

    Returns:
        4 by block_size/4 sized matrix of integers. 
    """
    byte_list = generate_random_key(block_size)
    return byte_list

def convert_to_state_matrix(lst):
    return [lst[i:i + 4] for i in range(0, len(lst), 4)]

def convert_hex_to_bytes(hex_str):
    """
    Take hex string and convert it to list of bytes

    Args:
        hex_str: hex string
    Returns:
        list of bytes
    """
    hex_str = hex_str[2:] if hex_str[:2] == "0x" else hex_str
    return list(bytes([int(hex_str[i:i+2],16) for i in range(0, len(hex_str), 2)]))

def convert_bytes_to_hex(bytes_list):
    """
    Take list of bytes and convert to hex string representation

    Args:
        byte_str: list(byte)
    Returns:
        hex string representation of the bstr
    """
    return ''.join(map("{:02x}".format, bytes_list))