Implementing Cryptography Using Python

Description

Learn to deploy proven cryptographic tools in your applications and services

Cryptography is, quite simply, what makes security and privacy in the digital world possible. Tech professionals, including programmers, IT admins, and security analysts, need to understand how cryptography works to protect users, data, and assets. Implementing Cryptography Using Python will teach you the essentials, so you can apply proven cryptographic tools to secure your applications and systems. Because this book uses Python, an easily accessible language that has become one of the standards for cryptography implementation, you’ll be able to quickly learn how to secure applications and data of all kinds.

In this easy-to-read guide, well-known cybersecurity expert Shannon Bray walks you through creating secure communications in public channels using public-key cryptography. You’ll also explore methods of authenticating messages to ensure that they haven’t been tampered with in transit. Finally, you’ll learn how to use digital signatures to let others verify the messages sent through your services.

• Learn how to implement proven cryptographic tools, using easy-to-understand examples written in Python
• Discover the history of cryptography and understand its critical importance in today’s digital communication systems
• Work through real-world examples to understand the pros and cons of various authentication methods
• Protect your end-users and ensure that your applications and systems are using up-to-date cryptography

Table of Contents

1. Introduction xvii
2. Chapter 1 Introduction to Cryptography and Python 1
   1. Exploring Algorithms 2
   2. Why Use Python? 2
   3. Downloading and Installing Python 3
   4. Installing on Ubuntu 4
   5. Installing on macOS 4
   6. Installing on Windows 4
   7. Installing on a Chromebook 4
   8. Installing Additional Packages 5
   9. Installing Pip, NumPy, and Matplotlib 6
   10. Installing the Cryptography Package 7
   11. Installing Additional Packages 8
   12. Testing Your Install 9
   13. Diving into Python Basics 9
   14. Using Variables 10
   15. Using Strings 11
   16. Introducing Operators 11
   17. Understanding Arithmetic Operators 11
   18. Understanding Comparison Operators 13
   19. Understanding Logical Operators 13
   20. Understanding Assignment Operators 14
   21. Understanding Bitwise Operators 15
   22. Understanding Membership Operators 15
   23. Understanding Identity Operators 16
   24. Using Conditionals 16
   25. Using Loops 17
   26. for 17
   27. while 18
   28. continue 18
   29. break 18
   30. else 18
   31. Using Files 19
   32. Understanding Python Semantics 20
   33. Sequence Types 20
   34. Introducing Custom Functions 26
   35. Downloading Files Using Python 27
   36. Introducing Python Modules 28
   37. Creating a Reverse Cipher 29
   38. Summary 30
3. Chapter 2 Cryptographic Protocols and Perfect Secrecy 31
   1. The Study of Cryptology 32
   2. Understanding Cryptography 32
   3. Cryptography’s Famous Family: Alice and Bob 33
   4. Diffie-Hellman 34
   5. Data Origin Authentication 34
   6. Entity Authentication 35
   7. Symmetric Algorithms 36
   8. Asymmetric Algorithms 36
   9. The Needham-Schroeder Protocols 36
   10. The Otway-Rees Protocol 38
   11. Kerberos 39
   12. Multiple-Domain Kerberos 40
   13. X.509 41
   14. Formal Validation of Cryptographic Protocols 46
   15. Configuring Your First Cryptographic Library 47
   16. Understanding Cryptanalysis 47
   17. Brute-Force Attacks 47
   18. Side-Channel Attacks 48
   19. Social Engineering 48
   20. Analytical Attacks 48
   21. Frequency Analysis 48
   22. Attack Models 49
   23. Shannon’s Theorem 50
   24. One-Time Pad 51
   25. XOR, AND, and OR 51
   26. One-Time Pad Function 56
   27. One-Way Hashes 58
   28. Cryptographic One-Way Hashes 59
   29. Message Authentication Codes 60
   30. Perfect Forward Secrecy 60
   31. Published and Proprietary Encryption Algorithms 61
   32. Summary 62
   33. References 62
4. Chapter 3 Classical Cryptography 65
   1. Password Best Practices 66
   2. Password Storage 66
   3. Hashing Passwords 67
   4. Salting Passwords 67
   5. Stretching Passwords 68
   6. Password Tools 68
   7. Obfuscating Data 69
   8. ASCII Encoding 70
   9. Base64 Encoding Text 70
   10. Binary Data 72
   11. Decoding 72
   12. Historical Ciphers 72
   13. Scytale of Sparta 73
   14. Substitution Ciphers 73
   15. Caesar Cipher 74
   16. ROT-13 76
   17. Atbash Cipher 77
   18. Vigenère Cipher 77
   19. Playfair 79
   20. Hill 2×2 83
   21. Column Transposition 87
   22. Affine Cipher 90
   23. Summary 93
5. Chapter 4 Cryptographic Math and Frequency Analysis 95
   1. Modular Arithmetic and the Greatest Common Devisor 96
   2. Prime Numbers 97
   3. Prime Number Theorem 98
   4. School Primality Test 98
   5. Fermat’s Little Theorem 100
   6. Miller-Rabin Primality Test 100
   7. Generate Large Prime Numbers 104
   8. Basic Group Theory 106
   9. Orders of Elements 107
   10. Modular Inverses 109
   11. Fermat’s Little Theorem to Find the Inverse 110
   12. Extending the GCD 111
   13. Euler’s Theorem 111
   14. Pseudorandomness 115
   15. Breaking C’s rand() Function 116
   16. Solving Systems of Linear Equations 117
   17. Frequency Analysis 120
   18. Cryptanalysis with Python 123
   19. Using an Online Word List 125
   20. Determining the Frequency 126
   21. Breaking the Vigenère Cipher 129
   22. Summary 138
6. Chapter 5 Stream Ciphers and Block Ciphers 139
   1. Convert between Hexdigest and Plaintext 140
   2. Use Stream Ciphers 141
   3. ARC4 147
   4. Vernam Cipher 148
   5. Salsa20 Cipher 149
   6. ChaCha Cipher 151
   7. Use Block Ciphers 156
   8. Block Modes of Operations 158
   9. ECB Mode 158
   10. CBC Mode 159
   11. CFB Mode 160
   12. OFB Mode 162
   13. CTR Mode 163
   14. Tricks with Stream Modes 164
   15. DIY Block Cipher Using Feistel Networks 165
   16. Advanced Encryption Standard (AES) 167
   17. Using AES with Python 167
   18. File Encryption Using AES 169
   19. File Decryption Using AES 169
   20. Summary 169
7. Chapter 6 Using Cryptography with Images 171
   1. Simple Image Cryptography 171
   2. Images and Cryptography Libraries 174
   3. Understanding the Cryptography Library 174
   4. Understanding the Cryptosteganography Library 175
   5. Image Cryptography 175
   6. File Cryptography Using Fernet 176
   7. Image Cryptography Using Fernet 179
   8. AES and Block Modes of Operations 180
   9. Exploring a Simple ECB Mode Example 181
   10. Exploring a Simple CBC Mode Example 185
   11. Applying the Examples 186
   12. Steganography 187
   13. Storing a Message Inside an Image 188
   14. Storing a Binary File Inside an Image 192
   15. Working with large images 195
   16. Summary 197
8. Chapter 7 Message Integrity 199
   1. Message Authentication Codes 200
   2. Hash-based Message Authentication Code 201
   3. Using HMAC to Sign Message 202
   4. Message Digest with SHA 203
   5. Binary Digests 204
   6. NIST Compliance 205
   7. CBC-MAC 206
   8. Birthday Attacks 207
   9. Crafting Forgeries 209
   10. The Length Extension Attack 209
   11. Setting Up a Secure Channel 210
   12. Communication Channels 211
   13. Sending Secure Messages over IP Networks 212
   14. Create a Server Socket 212
   15. Create a Client Socket 213
   16. Create a Threaded Server with TCP 214
   17. Adding Symmetric Encryption 215
   18. Concatenate Message and MAC 218
   19. Summary 221
   20. References 222
9. Chapter 8 Cryptographic Applications and PKI 223
   1. The Public-Key Transformation 224
   2. Exploring the Basics of RSA 226
   3. Generating RSA Certificates 229
   4. Constructing Simple Text Encryption and Decryption with RSA Certificates 231
   5. Constructing BLOB Encryption and
   6. Decryption with RSA Certificates 232
   7. The El-Gamal Cryptosystem 235
   8. Elliptic Curve Cryptography 238
   9. Generating ECC Keys 240
   10. Key Lengths and Curves 241
   11. Diffie-Hellman Key Exchange 242
   12. Summary 245
10. Chapter 9 Mastering Cryptography Using Python 247
    1. Constructing a Plaintext Communications Application 248
    2. Creating a Server 248
    3. Creating the Client 250
    4. Creating the Helper File 251
    5. Execution 252
    6. Installing and Testing Wireshark 253
    7. Implementing PKI in the Application Using RSA Certificates 255
    8. Modifying the Server 256
    9. Modifying the Client 257
    10. Modifying the Helper File 258
    11. Execution 259
    12. Implementing Diffie-Hellman Key Exchange 261
    13. Modifying the Server File 262
    14. Modifying the Client File 264
    15. Modifying the Helper File 266
    16. Creating the Diffie-Hellman Class File 270
    17. Execution 275
    18. Wrapping Up 276
    19. Index 277

Author Biography

SHANNON W. BRAY CASP, Security +, CISM is the Virtual CISO at Secured Systems providing clients guidance on establishing and maintaining information security plans, policies, procedures, standards, and guidelines using accepted frameworks. He has worked in this roles and others in corporations and federal agencies. Shannon has an MS in Cybersecurity from the University of Delaware. Prior to transitioning to cybersecurity, he was a well known IT expert with several successful books about Microsoft SharePoint.