`circom-helper`

circom-helper allows developers to test circom circuits quickly and easily.

It compiles circuits and exposes a JSON-RPC API which allows developers to generate witnesses and access signal values without writing command-line glue scripts.

Done:

witness generation endpoint
signal index lookup endpoint

Installation

npm i circom-helper

To build from source:

git clone git@github.com:weijiekoh/circom-helper.git && \
cd circom-helper && \
npm i && \
npm run build

Install dependencies:

sudo apt-get install libgmp-dev nlohmann-json3-dev nasm g++

User guide

Create a config file. Use config.example.json as a reference. The circuitDirs field should be an array of directories which contain the circom files you wish to compile. Note that there should not be any filename collisions, even across directories. Additionally, ensure that you install circom, snarkjs, circom_runtime, and ffiasm in your project's node_modules, and check their paths in the config file.
Create a compiled/ and temp/ directory for compiled circuits and tempoary files.
Run the server:

node build/index.js -c ./config.example.json -b ./compiled/ -p 9000 -nc

JSON-RPC API

gen_witness

Generates a witness given a circuit name and public inputs.

Inputs:

circuit: the name of the circuit. For example, if test.circom is in one of the circuitDirs, and you want to generate a witness for inputs to this circuit, set this value as test.
inputs: the public inputs to the circuit (as a JS object). For example: { left: '1', right: '2' }. The number values should be strings as the JS safe integer limit is lower than the group order for BN254 and other elliptic curves used for ZK proofs.

Returns:

witness: an array of strings (e.g. [1, 3, 1, 2]).

To find the index of any signal (e.g. main.out), use get_signal_index. With this index, you can then look up this array and get the value of the signal.

get_signal_index