Witnesscalc Adapter

This project provides a Rust adapter for compiling and linking Circom circuit witness generator C++ sources into a native library for target platforms (e.g., mobile devices). It includes macros and functions to facilitate the integration of witness generation into Rust codebases.

[!INFO]
This project supports Circom v2.2.0 and above. For details on witness calculation, please see the witnesscalc-v2.2.0 branch.

Requirements

Dependencies

• Linux:

sudo apt install build-essential cmake m4 nasm libstdc++6

• MacOS:

brew install nasm

Usage

Include the crate in your Cargo.toml:

[dependencies]
witnesscalc-adapter = "0.1"

[build-dependencies]
witnesscalc-adapter = "0.1"

In build.rs, add the following code to compile the witness generator C++ sources (<circuit name>.cpp and <circuit name>.dat) into a native library and link to it:

witnesscalc_adapter::build_and_link("../path to directory containing your C++ sources");
// e.g. witnesscalc_adapter::build_and_link("../testdata");
// The directory should contain the following files:
// - <circuit name>.cpp
// - <circuit name>.dat

In your main code, use the witness macro to generate a witness for a given input:

witnesscalc_adapter::witness!(<circuit name>);
// e.g. witnesscalc_adapter::witness!(multiplier2);

Calculate the witness by using the <circuit name>_witness function.

let wtns = <circuit name>_witness(inputs_json_string)
// e.g. let wtns = multiplier2_witness("{\"a\": [\"2\"], \"b\": [\"3\"]}")

It will generate a wtns bytes array like the output of witnesscalc or snarkjs.

Convert the wtns to bigints by using the parse_witness_to_bigints function.

let witness = parse_witness_to_bigints(&wtns).unwrap();

Supported platforms

Linux

• x86_64 linux
• arm64 linux

MacOS

• aarch64-apple-darwin
• x86_64-apple-darwin

iOS

• aarch64-apple-ios
• aarch64-apple-ios-sim
• x86_64-apple-ios

Android

• aarch64-linux-android
• x86_64-linux-android

Community

• Website: zkmopro.com
• X account:
• Telegram group:

Acknowledgements

• Inspired by https://github.com/chancehudson/rust-witness. This adapter relies on the 0xPolygonID/witnesscalc library fork.
• The project is sponsored by PSE.