You do not need to have programming experience or any special computer. Any computer that can run Python can do these projects, and you don't need much math because we'll not be inventing new encryption techniques just to learn how to use the pre-existing standard ones that don't require anything more than very basic algebra.

You can download the example code files for this book from your account at www.packtpub.com. If you purchased this book elsewhere, you can visit www.packtpub.com/support and register to have the files emailed directly to you.

You can download the code files by following these steps:

1. Log in or register at www.packtpub.com.
2. Select the SUPPORT tab.
3. Click on Code Downloads & Errata.
4. Enter the name of the book in the Search box and follow the onscreen instructions.

Once the file is downloaded, please make sure that you unzip or extract the folder using the latest version of:

• WinRAR/7-Zip for Windows
• Zipeg/iZip/UnRarX for Mac
• 7-Zip/PeaZip for Linux

The code bundle for the book is also hosted on GitHub at https://github.com/PacktPublishing/Hands-On-Cryptography-with-Python. In case there's an update to the code, it will be updated on the existing GitHub repository.

We also have other code bundles from our rich catalog of books and videos available at https://github.com/PacktPublishing/. Check them out!

We also provide a PDF file that has color images of the screenshots/diagrams used in this book. You can download it here: https://www.packtpub.com/sites/default/files/downloads/HandsOnCryptographywithPython_ColorImages.pdf.

There are a number of text conventions used throughout this book.

CodeInText: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: "If we enter HELLO, it prints out the correct answer of KHOOR."

A block of code is set as follows:

alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
str_in = raw_input("Enter message, like HELLO: ")

n = len(str_in)
str_out = ""

for i in range(n):
   c = str_in[i]
   loc = alpha.find(c)
   print i, c, loc, 
   newloc = loc + 3
   str_out += alpha[newloc]
   print newloc, str_out

print "Obfuscated version:", str_out

Any command-line input or output is written as follows:

$ python

Bold: Indicates a new term, an important word, or words that you see onscreen. For example, words in menus or dialog boxes appear in the text like this. Here is an example: "Select System info from the Administration panel."