Cracking Secret Codes with Python is a hands-on introduction to Python that teaches readers how to make and hack cipher programs, which are used to encrypt secret messages. Like the author's previous best-selling title, Automate the Boring Stuff with Python, this book offers readers real, interesting programs to cut their teeth with. Cracking Secret Codes with Python covers ciphers like the Caesar cipher, transposition cipher, and the RSA cipher, and teaches readers how to test and hack them. For every program, Sweigart provides the full source code and then walks readers through it, explaining how every line works. Along the way, readers will learn Python fundamentals like loops, variables, strings, lists, and functions--and by the book's end, they'll have a solid foundation in Python and some fun programs under their belt. 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 Vigen re 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:
Introduction Chapter 1: Making Paper Cryptography Tools Chapter 2: Installing Python Chapter 3: The Interactive Shell Chapter 4: Strings and Writing Programs Chapter 5: The Reverse Cipher Chapter 6: The Caesar Cipher Chapter 7: Hacking the Caesar Cipher with the Brute-Force Technique Chapter 8: Encrypting with the Transposition Cipher Chapter 9: Decrypting with the Transposition Cipher Chapter 10: Programming a Program to Test Our Program Chapter 11: Encrypting and Decrypting Files Chapter 12: Detecting English Programmatically Chapter 13: Hacking the Transposition Cipher Chapter 14: Making a Modular Arithmetic Module for the Multiplicative and Affine Ciphers Chapter 15: Programming the Affine Cipher Chapter 16: Hacking the Affine Cipher Chapter 17: The Simple Substitution Cipher Chapter 18: Hacking the Simple Substitution Cipher Chapter 19: The Vigenere Cipher Chapter 20: Frequency Analysis Chapter 21: Hacking the Viginere Cipher Chapter 22: The One-Time Pad Cipher Chapter 23: Finding Prime Numbers Chapter 24: Generating Keys for the RSA Cipher Chapter 25: Public Key Cryptography and Programming the RSA Cipher Appendix: Debugger