Skip to main content
Create, compile, and test a simple Circom scheme and verify a ZK-proof using the zk-SNARK Groth16 protocol.

​
Prerequisites

​
Initialize a project

1

Create a new project

npm create ton@latest ZkSimple && cd ZkSimple
2

Install libraries

npm install snarkjs @types/snarkjs
3

Install the verifier

npm install export-ton-verifier@latest

​
Create the Circom circuit

1

Create the circuit directory

mkdir -p circuits/Multiplier && cd circuits/Multiplier
2

Implement the circuit

This circuit proves knowledge of two numbers a and b, whose product is equal to the public output c, without revealing a and b themselves.
./circuits/Multiplier/Multiplier.circom
pragma circom 2.2.2;

template Multiplier() {
  signal input a;
  signal input b;

  signal output c;

  c <== a*b;
}

component main = Multiplier();
3

Compile the circuit

circom Multiplier.circom --r1cs --wasm --sym --prime bls12381
The compiler generates the following files:
  • Multiplier.r1cs — circuit constraints (R1CS)
  • Multiplier.sym — symbolic signal map
  • Multiplier.wasm — artifact for generating proof
4

Check the constraints

snarkjs r1cs info Multiplier.r1cs
snarkjs output
[INFO]  snarkJS: Curve: bls12-381
[INFO]  snarkJS: # of Wires: 4
[INFO]  snarkJS: # of Constraints: 1
[INFO]  snarkJS: # of Private Inputs: 2
[INFO]  snarkJS: # of Public Inputs: 0
[INFO]  snarkJS: # of Outputs: 1

​
Initialize trusted setup

The trusted setup is a one-time ceremony that generates the proving and verification keys for a circuit. It is called trusted because if the setup parameters are compromised, proofs could be forged.
  • For production use, participate in a multi-party trusted setup ceremony.
  • For local development and testing, a simplified single-party setup is sufficient.
Choose the “power of tau” parameter (10) as low as possible, because it affects execution time, but not too low, because the more constraints in the scheme, the higher the parameter required.
1

Execute the first phase

  snarkjs powersoftau new bls12-381 10 pot10_0000.ptau -v
  snarkjs powersoftau contribute pot10_0000.ptau pot10_0001.ptau --name="First contribution" -v -e="some random text"
2

Execute the second phase

  snarkjs powersoftau prepare phase2 pot10_0001.ptau pot10_final.ptau -v
  snarkjs groth16 setup Multiplier.r1cs pot10_final.ptau Multiplier_0000.zkey
  snarkjs zkey contribute Multiplier_0000.zkey Multiplier_final.zkey --name="1st Contributor" -v -e="some random text"
3

Export the verification key

snarkjs zkey export verificationkey Multiplier_final.zkey verification_key.json
4

Clean up artifacts

rm pot10_0000.ptau pot10_0001.ptau pot10_final.ptau Multiplier_0000.zkey

​
Export the verifier contract

1

Export the verifier contract

npx export-ton-verifier ./circuits/Multiplier/Multiplier_final.zkey ./contracts/verifier_multiplier.tolk --tolk
2

Generate TypeScript wrappers

The TypeScript wrappers enable type-safe interaction with the verifier contract.
npx export-ton-verifier import-wrapper ./wrappers/Verifier.ts --force

​
Test and verify the proof

1

Import dependencies

./tests/ZkSimple.spec.ts
import * as snarkjs from 'snarkjs';
import path from 'path';
import { dictFromInputList, groth16CompressProof } from 'export-ton-verifier';
import { Verifier } from '../wrappers/Verifier';
2

Implement local verification

const wasmPath = path.join(__dirname, '../circuits/Multiplier', 'Multiplier.wasm');
const zkeyPath = path.join(__dirname, '../circuits/Multiplier', 'Multiplier_final.zkey');
const verificationKey = require('../circuits/Multiplier/verification_key.json');

const input = { a: '342', b: '1245' };

const { proof, publicSignals } = await snarkjs.groth16.fullProve(input, wasmPath, zkeyPath);
const okLocal = await snarkjs.groth16.verify(verificationKey, publicSignals, proof);
3

Implement on-chain verification

const { pi_a, pi_b, pi_c, pubInputs } = await groth16CompressProof(proof, publicSignals);

// Quick check via get-method: verifies the proof locally without changing blockchain state.
expect(await verifier.getVerify({ pi_a, pi_b, pi_c, pubInputs })).toBe(true);

// Send the proof to the contract in a message.
// The contract will run verification; subsequent handling of the result depends on the integration.
await verifier.sendVerify(deployer.getSender(), { pi_a, pi_b, pi_c, pubInputs, value: toNano('0.15') });

​
Other languages

This tutorial follows the path: Circom → snarkjs → export-ton-verifier → TON. The same workflow applies to other stacks, the key requirement is to obtain a proof and a verification key in the snarkjs format. The idea is always the same: generate proof.json and verification_key.json in the snarkjs format, then perform the verification in TON with the export-ton-verifier. The zk-ton-examples repository contains templates for Noname, gnark, and Arkworks. It is possible to generate proofs in any of these stacks, then convert them to the snarkjs format and verify them both locally and on-chain.

​
Rust

Use the Arkworks library to generate the proof and verification key, then convert them into snarkjs format with ark-snarkjs.
1

Create a new project

cargo init
cargo add ark-bls12-381 ark-ff ark-groth16 ark-r1cs-std ark-relations ark-snark ark-snarkjs ark-std rand@0.8.5
2

Implement the circuit

Implement the circuit logic using Arkworks primitives, similar to a Circom circuit.
3

Compile, generate proof, perform trusted setup

Follow the same workflow as in the Circom section and the trusted setup section, but implement the logic in Rust with Arkworks instead of Circom. The resulting proof and verification key will be in Arkworks format, which can be converted to snarkjs format with ark-snarkjs.
4

Export the proof and verification key

The following script will create the directory and files automatically.
Rust
use ark_snarkjs::{export_proof, export_vk};
use ark_bls12_381::Bls12_381;

let _ = export_proof::<Bls12_381, _>(&proof, &public_inputs, "json/proof.json");
let _ = export_vk::<Bls12_381, _>(
    &params.vk,
    public_inputs.len(),
    "json/verification_key.json",
);
5

Export the verifier contract

npx export-ton-verifier ./circuits/Arkworks/MulCircuit/json/verification_key.json ./contracts/verifier_ark.tolk --tolk

​
Go

Use the gnark library to generate the proof and verification key, then convert them to the snarkjs format with gnark-to-snarkjs.
1

Create a new project

´´´bash mkdir zk-ton-gnark && cd zk-ton-gnark go mod init zk-ton-gnark

<Aside
  type="tip"
  >
  [The gnark repository](https://github.com/Consensys/gnark) contains an example circuit.

  [The zk-ton-examples repository](https://github.com/zk-examples/zk-ton-examples/tree/main/circuits/Cubic%20%28gnark%29) contains a working example of a simple cubic circuit.
</Aside>
</Step>

<Step
title="Install the dependencies"
>
```bash
go get github.com/consensys/gnark@latest
go get github.com/mysteryon88/gnark-to-snarkjs@latest
2

Export the proof and verification key

Go
{
  proof_out, _ := os.Create("proof.json")
  defer proof_out.Close()
  _ = gnarktosnarkjs.ExportProof(proof, []string{"35"}, proof_out)
}
{
  out, _ := os.Create("verification_key.json")
  defer out.Close()
  _ = gnarktosnarkjs.ExportVerifyingKey(vk, out)
}
3

Export the verifier contract

npx export-ton-verifier ./circuits/cubic-gnark/verification_key.json ./contracts/verifier_cubic.tolk --tolk
  • The zk-ton-examples repository contains additional examples of zk-SNARK circuits and their integration with TON.
  • The export-ton-verifier repository is a library that generates TON-compatible verifier contracts from snarkjs verification keys.
  • The snarkjs repository is a JavaScript library for generating and verifying zk-SNARK proofs, as well as performing trusted setup ceremonies.
  • The ark-snarkjs repository is a utility that converts Arkworks proofs and verification keys into a format compatible with snarkjs.
  • The gnark-to-snarkjs repository is a utility that converts gnark proofs and verification keys into a format compatible with snarkjs.
  • The Noname repository is a high-level language for writing zk-SNARK circuits, which can be compiled to a format compatible with snarkjs.
  • The gnark repository is a Go library for writing zk-SNARK circuits and generating proofs.
  • The Arkworks homepage is a Rust ecosystem for zk-SNARKs, providing libraries for writing circuits, generating proofs, and performing trusted setup ceremonies.