Bertie is a minimal, high-assurance implementation of TLS 1.3 written in a subset of Rust called hacspec. It is purely functional, verification-friendly, and designed to be succinct and minimal. Authored by Karthikeyan Bhargavan, Bertie is not yet ready for public use but offers an example HTTPS client and server for testing purposes. Working on Bertie involves using hacspec, a more restrictive version of Rust, and ensuring all code is valid according to hacspec. The project is inspired by prior research works on hacspec and TLS 1.3. Bertie is licensed under Apache 2.0 and supported by Inria and the nlnet foundation.
https://github.com/cryspen/bertie