Table of Contents for
Hands-On Cryptography with Python

Version ebook / Retour

Cover image for bash Cookbook, 2nd Edition Hands-On Cryptography with Python by Samuel Bowne Published by Packt Publishing, 2018
  1. Hands-On Cryptography with Python
  2. Title Page
  3. Copyright and Credits
  4. Hands-On Cryptography with Python
  5. Packt Upsell
  6. Why subscribe?
  7. PacktPub.com
  8. Contributor
  9. About the author
  10. Packt is searching for authors like you
  11. Table of Contents
  12. Preface
  13. Who this book is for
  14. What this book covers
  15. To get the most out of this book
  16. Download the example code files
  17. Download the color images
  18. Conventions used
  19. Get in touch
  20. Reviews
  21. Obfuscation
  22. About cryptography
  23. Installing and setting up Python
  24. Using Python on Mac or Linux
  25. Installing Python on Windows
  26. Caesar cipher and ROT13
  27. Implementing the Caesar cipher in Python
  28. ROT13
  29. base64 encoding
  30. ASCII data
  31. Binary data
  32. XOR
  33. Challenge 1 – the Caesar cipher
  34. Challenge 2 – base64
  35. Challenge 3 – XOR
  36. Summary
  37. Hashing
  38. MD5 and SHA hashes
  39. What are hashes?
  40. Windows password hashes
  41. Getting hashes with Cain
  42. MD4 and Unicode
  43. Cracking hashes with Google
  44. Cracking hashes with wordlists
  45. Linux password hashes
  46. Challenge 1 – cracking Windows hashes
  47. Challenge 2 – cracking many-round hashes
  48. Challenge 3 – cracking Linux hashes
  49. Summary
  50. Strong Encryption
  51. Strong encryption with AES
  52. ECB and CBC modes
  53. ECB
  54. CBC
  55. Padding oracle attack
  56. Strong encryption with RSA
  57. Public key encryption
  58. RSA algorithm
  59. Implementation in Python
  60. Challenge – cracking RSA with similar factors
  61. Large integers in Python
  62. What's next?
  63. Cryptography within IoT
  64. ZigBee cryptographic keys
  65. Complexity of ZigBee key management
  66. Bluetooth – LE
  67. Summary
  68. Other Books You May Enjoy
  69. Leave a review - let other readers know what you think

ROT13

ROT13 is nothing more than a Caesar cipher with a shift equal to 13 characters. In the script that follows, we will hardcode the shift to be 13. If you run one cycle of ROT13, it changes HELLO to URYYB, and if you encrypt it again with the same process, putting in that URYYB, it'll turn back into HELLO, because the first shift is just by 13 characters and shifting by another 13 characters takes the total shift to 26, which wraps right around, and that is what makes this one useful and important:

  1. Now let's look at the ROT13 script using the following command:
$ nano rot13.py
  1. When you run the preceding command, you can see the script file:
  1. It's just exactly equal to our last Caesar cipher shift, with a script with a shift of 13. Run the script as shown here:
$ python rot13.py

The following is the output:

  1. If we enter the message URYYB and run that, it turns back into HELLO:

This is important because there are quite a few cryptographic functions that have this property; where you encrypt something once and encrypt it again, you reverse the process. Instead of making it more encrypted, it becomes unencrypted. In the next section, we will cover base64 encoding.