Implementing-cryptography-using-python

Chapter 1 ■ Introduction to Cryptography and Python 3
this book will work. If you are on a Mac, you can use the Terminal app found
inside the Utilities folder. On a Windows machine, you have several options
as well: you can install a number of tools such as Cygwin, Visual Studio, or
PyCharm; use the Windows 10 Linux subsystem; or just install Ubuntu Linux
from the Microsoft Store. If you are new to Linux, I recommend practicing your
command-line skills a bit to help get you comfortable.
When you start the Python shell (by typing python or python3 at the command
line), you will see the version and the date associated with the version. For instance,
if you install and run Python in a Linux environment, you should see
something similar to the following:
Python 3.7.4+ (default, Sep 4 2019, 08:03:05)
[GCC 9.2.1 20190827] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>
The majority of Python interpreters use >>> as a prompt to accept user input;
one notable exception is IPython, which is discussed briefly in a moment. Once
you are in a Python shell, exit by pressing CTRL+D or typing exit(). Python
files use a .py extension, and we start their execution in Linux environments
by typing python3 filename.py; (keep in mind that you still need to chmod
+x the file).
NOTE In Unix-like operating systems, the chmod command sets the permissions
of files or directories.
As you will learn later in this chapter, a large number of modules are available
for Python, many of which we will use along your journey of learning
cryptography. One of the more notable modules you will learn more about is
NumPy. NumPy offers numerical operations to Python, including fast multidimensional
array operations, random number generation, and linear algebra.
Another module that you will be introduced to is Matplotlib, which is an excellent
library for plotting. In Chapter 6, you will learn more about PyFITS, which
is a module that provides access to Flexible Image Transport System (FITS) files.
FITS is a portable file standard that is widely used throughout the astronomy
community to store images and tables. We will be combining it with our cryptography
techniques to encrypt and decrypt image files.
Downloading and Installing Python
You can download the Python interpreter from www.python.org/python, where
you’ll find versions for Ubuntu, macOS, and Windows. Be sure to download
version 3.7 or higher, since Python 2 is now unsupported.