Skip to content


Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?

Latest commit



Failed to load latest commit information.
Latest commit message
Commit time
February 23, 2023 12:46
March 4, 2023 19:14
May 23, 2023 11:39
May 17, 2023 23:57
February 23, 2023 12:46
January 13, 2021 09:04
February 9, 2023 10:58
September 6, 2022 15:27
November 5, 2022 14:09
June 16, 2017 17:01
November 5, 2022 14:09
May 17, 2023 23:02
December 1, 2022 14:58
September 6, 2022 15:56
December 1, 2022 16:36
February 23, 2023 11:44

A High-Assurance Cryptographic Library

This repository contains verified code for a library of modern cryptographic algorithms, including Curve25519, Ed25519, AES-GCM, Chacha20, Poly1305, SHA-2, SHA-3, HMAC, and HKDF. This set of algorithms is enough to support the full NaCl API and several TLS 1.3 ciphersuites. The code for all of these algorithms is formally verified using the F* verification framework for memory safety, functional correctness, and secret independence (resistance to some types of timing side-channels).

Documentation: More detailed documentation on the library and our verification method can be found at

The code in this repository is divided into three closely-related sub-projects, all developed as part of Project Everest.


HACL* is a formally verified library of modern cryptographic algorithms written in a subset of F* called Low* and compiled to C using a compiler called KaRaMeL. The Low* source code for each primitive is verified for memory safety, functional correctness, and secret independence. The compiler generates efficient, readable, standalone C code for each algorithm that can be easily integrated into any C project. We include the current C code for various HACL* algorithms in the dist directory. HACL* can also be compiled to WebAssembly.


ValeCrypt provides formally verified high-performance cryptographic code for selected primitives in assembly language. It relies on the Vale tool to produce code and proofs in F*. Vale supports multiple platforms and proves that its implementations are memory safe, functionally correct, and that timing and memory accesses are secret independent.


EverCrypt is a high-performance, cross-platform, formally verified modern cryptographic provider that packages implementations from HACL* and ValeCrypt, and automatically picks the fastest one available, depending on processor support and the target execution environment (multiplexing). Furthermore, EverCrypt offers an (agile) API that makes it simple to switch between algorithms (e.g., from SHA2 to SHA3).


Warning: This is a research project. Although some of our code is currently used in popular products like Mozilla Firefox and Wireguard, we highly recommend that users consult with the HACL* maintainers before using this code in production systems.

We are actively developing and integrating our code on the master branch, which tracks F*'s master branch. Ongoing developments on new cryptographic primitives happen in the dev branch, which runs a little ahead of master. You can find a current snapshot of our C and assembly code in the dist directory; stable releases of the full library can be found in the releases page.


All the code in this repository is released under an Apache 2.0 license. The generated C code from HACL* is also released under an MIT license. Contact the maintainers if you have other licensing requirements.

Contact or Contribute

This repository contains contributions from many students and researchers at INRIA, Microsoft Research, and Carnegie Mellon University, and it is under active development. The primary authors of each verified algorithm are noted in the corresponding file. For questions and comments, or if you want to contribute to the project, contact the current maintainers at