zkkit witness

Generate a witness file from circuit inputs

Description

The witness command wraps snarkjs to generate a witness file by executing your compiled circuit with provided input values. The witness contains all intermediate wire values needed for proof generation.

Under the hood: This command runs snarkjs wtns calculate [wasm] [input] outputs/[witness]

Usage

bash

zkkit witness [circuit-name] [input-file]

Examples

Generate witness from an input JSON file:

bash

zkkit witness multiplier input.json

Example input.json format:

{
  "a": "3",
  "b": "5"
}

Output

This command generates a witness.wtns file containing all the wire values computed during circuit execution.

Implementation

View how this command works under the hood:

src/commands/witness.js

import { run } from "../utils/exec.js";

export default async function witness(opts = {}) {
  const input = opts.input || "inputs/inputs.json";
  const name = opts.name || "witness.wtns";

  // Use snarkjs to generate witness
  await run(
    `snarkjs wtns calculate outputs/schema_js/schema.wasm ${input} outputs/${name}`
  );

  console.log(`✔ Witness generated: outputs/${name}`);
}

What it does:

Accepts input JSON path (defaults to inputs/inputs.json)
Accepts witness output name (defaults to witness.wtns)
Uses snarkjs to calculate witness from the compiled WASM binary
Evaluates the circuit with the provided input values
Saves the witness file to outputs/ directory