Summary

In this chapter, we covered hashing, the first of the cryptographic operations we will be exploring in this book. Hashing functions can be used by developers for a variety of purposes: in particular, we've looked at SHA-2 as the recommended function for calculating digests of files and messages (to verify their integrity or to generate identifiers), and Argon2 and scrypt for storing passwords and deriving encryption keys. We've also looked at the issues that impact hashing functions, and why older algorithms are to be avoided.

In the next chapter, we're going to cover encryption and decryption using symmetric ciphers, the first of the two kinds we'll be studying in this book, using two popular algorithms – AES and ChaCha20-Poly1305. We'll also put what we saw in this chapter into practice and use hashing functions to derive symmetric encryption keys safely.