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 OS dependencies

On Debian, Ubuntu, or derivatives:

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

On openSUSE or derivatives:

sudo zypper install gmp-devel nlohmann_json-devel nasm g++

User guide

1. 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.

2. Create a compiled/ and temp/ directory for compiled circuits and
   tempoary files.

3. Run the server:

    npm run serve
   

4. Run the internal test suite for the server:

    npm run test-server
   

5. Run a test suite for the example circuit under example/:

    npm run test-snarks
   

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

Inputs:

• circuit: the name of the circuit.
• name: the signal name (e.g. main.out).

Returns:

• index: a numeric value as a string.