Circom Workflow Automation

This repository contains automated scripts for working with Circom circuits, from compilation to proof generation and verification.

Scripts

1. circom_workflow.sh - Complete Workflow

This script automates the entire circom workflow from compilation to proof generation.

Usage:

./circom_workflow.sh <circuit_filename>

Example:

./circom_workflow.sh multiplier2.circom

What it does:

1. Compiles the circom circuit with all necessary outputs (--r1cs --wasm --sym --c)
2. Sets up the JavaScript directory and witness generation
3. Performs the Powers of Tau ceremony (if not already done)
4. Executes Phase 2 setup (circuit-specific trusted setup)
5. Generates a zk-proof using Groth16
6. Verifies the proof
7. Generates a Solidity verifier contract
8. Shows call parameters for smart contract verification

2. generate_proof.sh - Quick Proof Generation

This script is for when you already have the circuit compiled and setup done, and just want to generate new proofs with different inputs.

Usage:

./generate_proof.sh <circuit_filename> [input_file]

Examples:

./generate_proof.sh multiplier2.circom                    # Uses default input.json
./generate_proof.sh multiplier2.circom custom_input.json  # Uses custom input file

What it does:

1. Computes witness with the provided input
2. Generates a zk-proof
3. Verifies the proof
4. Shows proof summary and smart contract call parameters

Prerequisites

Make sure you have the following tools installed:

• Circom
• snarkjs
• Node.js
• jq (for JSON formatting)

Install snarkjs:

npm install -g snarkjs

File Structure

After running the complete workflow, you'll have:

your-circuit.circom              # Your circuit file
your-circuit.r1cs               # Constraint system
your-circuit.sym                # Symbols file
input.json                      # Circuit inputs (main directory)
verifier.sol                    # Solidity verifier contract (main directory)
your-circuit_cpp/               # C++ files (if using --c flag)
your-circuit_js/                # JavaScript directory containing:
  ├── your-circuit.wasm         # WebAssembly circuit
  ├── generate_witness.js       # Witness generator
  ├── witness.wtns             # Computed witness
  ├── pot12_*.ptau             # Powers of tau files
  ├── your-circuit_*.zkey      # Zero-knowledge keys
  ├── verification_key.json    # Verification key
  ├── proof.json              # Generated proof
  └── public.json             # Public inputs/outputs

Input Format

Your input file should be a JSON object with the circuit's input signals:

{
  "a": "3",
  "b": "11"
}

For the multiplier2 circuit, this proves that 3 * 11 = 33.

Smart Contract Deployment

After running the scripts, you can deploy the generated Solidity verifier:

1. Copy the content of verifier.sol (located in the main directory)
2. Deploy it on your preferred network (testnet recommended for testing)
3. Use the call parameters shown by the script with the verifyProof function

The verifyProof function will return true if the proof is valid.

Example: Multiplier2 Circuit

The included multiplier2.circom circuit proves knowledge of two factors of a number:

pragma circom 2.0.0;

template Multiplier2() {
    signal input a;
    signal input b;
    signal output c;
    c <== a*b;
}

component main = Multiplier2();

This circuit proves that you know two numbers a and b such that a * b = c, without revealing a and b.

Troubleshooting

1. "Command not found" errors: Make sure circom and snarkjs are installed and in your PATH
2. "File not found" errors: Ensure your circuit file exists and you're running the script from the correct directory
3. Permission denied: Make sure the scripts are executable (chmod +x script_name.sh)
4. Node.js errors: Ensure Node.js is installed and the witness calculator files are present

Security Note

The Powers of Tau ceremony in these scripts is for development/testing purposes only. For production use, you should:

1. Use a more secure ceremony
2. Participate in a trusted setup with multiple contributors
3. Use larger parameter sizes for stronger security