hax is a tool for high assurance translations that translates a large subset of Rust into formal languages such as F* or Coq. This extends the scope of the hacspec project, which was previously a DSL embedded in Rust, to a usable tool for verifying Rust programs.

So what is hacspec now?

hacspec is the functional subset of Rust that can be used, together with a hacspec standard library, to write succinct, executable, and verifiable specifications in Rust. These specifications can be translated into formal languages with hax.

Hax is a cargo subcommand. The command cargo hax accepts the following subcommands:

• into (cargo hax into BACKEND): translate a Rust crate to the backend BACKEND (e.g. fstar, coq).
• json (cargo hax json): extract the typed AST of your crate as a JSON file.

Note:

• BACKEND can be fstar, coq or easycrypt. cargo hax into --help gives the full list of supported backends.
• The subcommands cargo hax, cargo hax into and cargo hax into <BACKEND> takes options. For instance, you can cargo hax into fstar --z3rlimit 100. Use --help on those subcommands to list all options.

Hax indenteds to support full Rust, with the two following exceptions, promoting a functional style:

1. no unsafe code (see cryspen#417);
2. mutable references (aka &mut T) on return types or when aliasing (see cryspen#420).

Each unsupported Rust feature is documented as an issue labeled unsupported-rust. When the issue is labeled wontfix-v1, that means we don't plan on supporting that feature soon.

Quicklinks:

• 🔨 Rejected rust we want to support;
• 💭 Rejected rust we don't plan to support in v1.

There's a set of examples that show what hax can do for you. Please check out the examples directory.

Just clone & cd into the repo, then run nix develop .. You can also just use direnv, with editor integration.

• rust-frontend/: Rust library that hooks in the rust compiler and extract its internal typed abstract syntax tree THIR as JSON.
• engine/: the simplication and elaboration engine that translate programs from the Rust language to various backends (see engine/backends/).
• cli/: the hax subcommand for Cargo.

You can use the .utils/rebuild.sh script (which is available automatically as the command rebuild when using the Nix devshell):

• rebuild: rebuild the Rust then the OCaml part;
• rebuild TARGET: rebuild the TARGET part (TARGET is either rust or ocaml).

• 📕 Tech report
• 📕 HACSpec: A gateway to high-assurance cryptography
• 📕 Original hacspec paper

• 📕 Last yard

Before starting any work please join the Zulip chat, start a discussion on Github, or file an issue to discuss your contribution.