Full Stack Python Security

3 Keyed hashing

This chapter covers

• Generating a secure key
• Verifying data authentication with keyed hashing
• Using the hmac module for cryptographic hashing
• Preventing timing attacks

In the previous chapter, you learned how to ensure data integrity with hash functions. In this chapter, you’ll learn how to ensure data authentication with keyed hash functions. I’ll show you how to safely generate random numbers and passphrases. Along the way, you’ll learn about the os, secrets, random, and hmac modules. Finally, you learn how to resist timing attacks by comparing hash values in length-constant time.

3.1 Data authentication

Let’s revisit Alice’s document management system from the previous chapter. The system hashes each new document before ...