def __shift_rows(message):
    """
        Input: message - List of lists (4x4 Matrix)

        Output: message - List of lists (4x4 Matrix)

        ShiftRows step of the algorithm. This step rotates elements in rows each by different
        amount depending on the row. First row stays the same, second is rotated to the left by one
        third is rotated to the left by two, and fourth is rotated to the left by three.
    """
    for i in range(4):
        message[i] = message[i][i:] + message[i][:i]
    return message
