Implementing-cryptography-using-python

2 Chapter 1 ■ Introduction to Cryptography and Python
Exploring Algorithms
The algorithms you will explore in this book can be quite sophisticated, but
most of the logic is encapsulated into little black boxes that allow you to interface
with the algorithms using functions. In the programming or mathematical
world, a function is merely a way to enter values and receive output. When using
algorithms in cryptography, we generally have two inputs for encryption and
two inputs for decryption:
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The encryption process will take the plaintext message (P) along with an
encryption key (K) and then run the plaintext through encryption algorithms,
which will return ciphertext (C).
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On the decryption side, the ciphertext (C) will be supplied along with the
encryption key (K), which will produce the plaintext (P) message.
As you study various encryption themes throughout this book, you will find
that they are described by three algorithms: GEN for key generation, ENC for
the encryption algorithm, and DEC for the decryption algorithm. You’ll revisit
this concept at the end of this chapter when you learn how to create a Python
function.
Why Use Python?
Using Python for cryptography is simpler than using languages such as C or
C++; while free libraries such as OpenSSL are available, their use can be quite
complex. Python removes these complexities with many built-in libraries that
aid in cryptography scripting. It is also a great choice because Python is free in
terms of license. Python can be described as an open-source, general-purpose
language that is object oriented, functional, and procedural, and it allows for
the interface with C/ObjC/Java/Fortran and even .NET. A number of versions
are available, from 2.5.x through 3.x. Currently, 3.x is becoming more popular
as new libraries are introduced. Python comes preinstalled with Linux and
macOS, and you can install it on Windows as well. You will learn how to install
Python in each of these environments later in this chapter.
Because Python is available for Windows, Linux/Unix, Mac, and Chromebooks,
among others, the lessons you learn here will be portable to several
environments. Python has proven to be quite powerful in information security
and can be used to quickly script solutions to help you become a better security
practitioner. If you are using Ubuntu Linux, every command you see in