Symmetric encryption with ChaCha20-Poly1305
ChaCha20 is a more recent symmetric cipher designed by Daniel J. Bernstein in the mid-'00s. It's often used together with the Poly1305 hashing function (in this case, it's also called "message authentication code"), which was designed by the same cryptographer. The result of the combination of the two is the ChaCha20-Poly1305 authenticated stream cipher.
We talked about authenticated stream ciphers in the previous section when referring to AES-GCM: functionally, ChaCha20-Poly1305 serves the same purpose. Even in practice, they are used very similarly, as you'll see in the samples in this section.
ChaCha20-Poly1305 has been seeing an increase in interest and popularity in recent years since it's now implemented by a variety of applications and, more frequently, as a cipher for the TLS protocol (used by HTTPS). For example, Google offers support for it in all of its online services and in the Android...
