The new generation of Transport Layer Security (TLS 1.3) incorporates several new features that make internet traffic more secure, including encrypting handshake messages to keep certificates private, redesigning the way secret keys are derived, and a zero round-trip connection setup, which makes certain requests faster than TLS 1.2. Every day, more than a billion people use Facebook to connect with their friends and family - and TLS 1.3 secures their data in transit from apps to our servers. To implement TLS 1.3 here at Facebook, we built Fizz, a robust, highly performant TLS library written in C++ 14. In addition to the protocol enhancements that come with TLS 1.3, Fizz offers a number of implementation features, including support for asynchronous I/O by default, and scatter/gather I/O to eliminate the need for extra copies of data.

https://code.fb.com/networking-traffic/deploying-tls-1-3-at-scale-with-fizz-a-performant-open-source-tls-library/ https://github.com/facebookincubator/fizz