rust-circom-experimental

An experimental port of IDEN3 circom compiler to rust.

❗ This is not the official and supported implementation of IDEN3 circom and circomlib circuits please use official version instead

Building

Install rust

curl https://sh.rustup.rs -sSf | sh

Install additional dependencies, you may need to install the clang build-essentials and openssl-dev

Clone the repo

git clone https://github.com/iden3/rust-circom-experimental.git

Build

cargo build --release

The final binary will be in /target/release/circom2

Usage

Generating trusted setup

circom2 setup --circuit <circut.circom> --pk <proving.key> --verifier <verifier.sol>

• circuit.circom is an input file with the main component that specifies the circuit
• proving.key if a generated output with the key required to generate proofs
• verifier.sol if a generated output with the smartcontract to verify the generated proofs

if you want to do a test, create a file with name circuit.circom with the following contents and run the circom2 setup

template T() {
    signal private input p;
    signal private input q;
    signal output r;

    r <== p*q;
}
component main = T();

Generating a proof

circom2 prove --circuit <circuit.circom> --input <input.json> --pk <proving.key> --proof <proof.json>

• circuit.circom is an input file with the main component that specifies the circuit
• input.json is an input file with the required input signals to generate the full witness
• proving.key if an input file with the key required to generate proofs
• proof.json the input required to the smartcontract to verify the proof

if you want to do a test, create a file with name input.circom with the following contents and run the circom2 prove

{ a : 2, b: 3 }

then deploy the verifier.sol smartcontract and exec the verifyTx method with the contents of the proof.json

Testing a circuit

In order to test if a circuit is correct is possible to write an embedded test by using the #[test] tag before a template definition (see interop/circomlib/babyjub.circom), to execute the test, run:

• circom2 test --circuit <circuit.circom>

this will run the tests found in the circuit and all the tests found in the included templates

Javascript bindings

to compile the javascript bindings, go to the binding/js folder and run:

• npm i
• npm run install
• npm test

check the test located in binding/js/test/test.js

Flutter bindings

The code is based on https://github.com/mimirblockchainsolutions/flutter-rust-middleware

Prerequisites

• Rust
• Flutter
• cargo-lipo
• Android Studio
• NDK
• Xcode

Export vars

• export ANDROID_HOME=/Users/$USER/Library/Android/sdk
• export NDK_HOME=$ANDROID_HOME/ndk-bundle

Then, you need to run the ndk script to build your compile targets from the root folder of the project

./ndk.sh

Build

• Go to binding/flutter/cargo and run ./build.sh
• Go to binding/flutter and run
  • flutter build ios or
  • flutter build apk

Test

• Go to binding/flutter and run flutter run

Differences between official circom version

There are few differences between this implementation and the official circom:

• Precedence of operators rust-like instead C-like:
  • DECNUMBER, HEXNUMBER, "(" exp ")"
  • Unary - !
  • **
  • * / \\ %
  • + -
  • << >>
  • &
  • ^
  • |
  • == != < > <= >=
  • &&
  • ||
• Removed ++, -- and :?
• Matrix access is only accessible with [x][y] (not with [x,y])
• End statement semicolons are mandatory
• Loops/conditionals statements must be inside blocks { }
• Added dbg! function to trace variables, signals and components
• Do now allow to use component signal outputs until all signal input are set
• Signal input/outputs arrays should be evaluable with template parameters
• Stamements tagged with #[w] are only evaluated in witness generation
• #[test] tagged templates are used to verify embeeded tests