# Cracking Codes with Python: An Introduction to Building and Breaking Ciphers

- Length: 416 pages
- Edition: 1
- Language: English
- Publisher: No Starch Press
- Publication Date: 2018-01-23
- ISBN-10: 1593278225
- ISBN-13: 9781593278229
- Sales Rank: #34299 (See Top 100 Books)

Learn how to program in Python while making and breaking ciphers—algorithms used to create and send secret messages!

After a crash course in Python programming basics, you’ll learn to make, test, and hack programs that encrypt text with classical ciphers like the transposition cipher and Vigenère cipher. You’ll begin with simple programs for the reverse and Caesar ciphers and then work your way up to public key cryptography, the type of encryption used to secure today’s online transactions, including digital signatures, email, and Bitcoin.

Each program includes the full code and a line-by-line explanation of how things work. By the end of the book, you’ll have learned how to code in Python and you’ll have the clever programs to prove it!

**You’ll also learn how to:**

- Combine loops, variables, and flow control statements into real working programs
- Use dictionary files to instantly detect whether decrypted messages are valid English or gibberish
- Create test programs to make sure that your code encrypts and decrypts correctly
- Code (and hack!) a working example of the affine cipher, which uses modular arithmetic to encrypt a message
- Break ciphers with techniques such as brute-force and frequency analysis

There’s no better way to learn to code than to play with real programs. *Cracking Codes with Python* makes the learning fun!

### Table of Contents

Chapter 1: Making Paper Cryptography Tools

Chapter 2: Programming in the Interactive Shell

Chapter 3: Strings and Writing Programs

Chapter 4: The Reverse Cipher

Chapter 5: The Caesar Cipher

Chapter 6: Hacking the Caesar Cipher with Brute-Force

Chapter 7: Encrypting with the Transposition Cipher

Chapter 8: Decrypting with the Transposition Cipher

Chapter 9: Programming a Program to Test Your Program

Chapter 10: Encrypting and Decrypting Files

Chapter 11: Detecting English Programmatically

Chapter 12: Hacking the Transposition Cipher

Chapter 13: A Modular Arithmetic Module for the Affine Cipher

Chapter 14: Programming the Affine Cipher

Chapter 15: Hacking the Affine Cipher

Chapter 16: Programming the Simple Substitution Cipher

Chapter 17: Hacking the Simple Substitution Cipher

Chapter 18: Programming the Vigenère Cipher

Chapter 19: Frequency Analysis

Chapter 20: Hacking the Vigenère Cipher

Chapter 21: The One-Time Pad Cipher

Chapter 22: Finding and Generating Prime Numbers

Chapter 23: Generating Keys for the Public Key Cipher

Chapter 24: Programming the Public Key Cipher

Appendix: Debugging Python Code

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