Mina zkApp: Authenticity Zkapp

A zero-knowledge proof system for verifying image authenticity on the Mina blockchain.

Installation

npm install authenticity-zkapp

Deployment

Prerequisites

1. Install dependencies:

   npm install

2. Create a .env file with your private keys (see .env.example):

   # Devnet keys
   DEVNET_PAYER_PRIVATE_KEY=EKE...  # Account that pays transaction fees
   DEVNET_ZKAPP_PRIVATE_KEY=EKE...  # Deterministic zkApp deployment address
   
   # Mainnet keys
   MAINNET_PAYER_PRIVATE_KEY=EKE...
   MAINNET_ZKAPP_PRIVATE_KEY=EKE...
   
   # Zeko keys
   ZEKO_PAYER_PRIVATE_KEY=EKE...
   ZEKO_ZKAPP_PRIVATE_KEY=EKE...

Deploy to a Network

Deploy the AuthenticityZkApp contract:

# Deploy to devnet
npm run deploy:devnet

# Deploy to mainnet
npm run deploy:mainnet

# Deploy to zeko
npm run deploy:zeko

The deployment script will:

1. Compile the AuthenticityProgram (dependency)
2. Compile the AuthenticityZkApp contract
3. Deploy to the specified network
4. Save deployment info to deployments/[network]-deployment.json

Deployment Output

After successful deployment, you'll receive:

• Transaction hash for tracking
• zkApp address for contract interaction
• Explorer link to view the deployment

Example deployment info:

{
  "network": "devnet",
  "zkAppAddress": "B62qj2zKtjxv1oaY4S9f5Noy3BKj7V3SWHX91u4vwuCDwyQVbsTeNF5",
  "payerAddress": "B62qkifieqVmoequ7HrKisEPyFno14MP2fpAUnDYZ2krdMt7PbhtgG6",
  "deployedAt": "2025-08-13T19:10:01.180Z",
  "explorerUrl": "https://minascan.io/devnet/account/B62qj2zKtjxv1oaY4S9f5Noy3BKj7V3SWHX91u4vwuCDwyQVbsTeNF5",
  "txHash": "5JvGN4pCvZDJpykvKHXzAkrbfe3q55GkZamN8qmYSgsnwtv8MSjD"
}

Usage

Run the Example Script

npm run example

Basic Image Verification

import {
  AuthenticityProgram,
  AuthenticityInputs,
  FinalRoundInputs,
  prepareImageVerification,
  Bytes32
} from 'authenticity-zkapp';
import { PrivateKey, PublicKey, Signature } from 'o1js';

// 1. Compile the zkProgram
await AuthenticityProgram.compile();

// 2. Prepare image for verification
const verificationInputs = prepareImageVerification('path/to/image.jpg');

// 3. Create a signature to prove ownership
const privateKey = PrivateKey.random();
const publicKey = PublicKey.fromPrivateKey(privateKey);
const signature = Signature.create(
  privateKey, 
  verificationInputs.expectedHash.toFields()
);

// 4. Create public and private inputs
const publicInputs = new AuthenticityInputs({
  commitment: verificationInputs.expectedHash,
  signature,
  publicKey
});

const privateInputs = new FinalRoundInputs({
  state: verificationInputs.penultimateState,
  initialState: verificationInputs.initialState,
  messageWord: verificationInputs.messageWord,
  roundConstant: verificationInputs.roundConstant
});

// 5. Generate the proof
const { proof } = await AuthenticityProgram.verifyAuthenticity(
  publicInputs,
  privateInputs
);

// 6. Verify the proof
const isValid = await AuthenticityProgram.verify(proof);
console.log('Proof is valid:', isValid);

Computing On-Chain Commitment

To compute the exact commitment value that will be stored on-chain:

import { computeOnChainCommitment } from 'authenticity-zkapp';
import fs from 'fs';

const imageData = fs.readFileSync('path/to/image.jpg');
const commitment = computeOnChainCommitment(imageData);
console.log('On-chain commitment:', commitment.toString());

API Reference

Core Classes

• AuthenticityProgram: The main zkProgram for generating and verifying proofs
• AuthenticityProof: The proof type returned by the program
• AuthenticityInputs: Public inputs (commitment, signature, publicKey)
• FinalRoundInputs: Private inputs for SHA-256 final round verification
• Bytes32: 32-byte type for SHA-256 hashes
• AuthenticityZkApp: Smart contract for on-chain verification (stores Poseidon hash of commitment)

Helper Functions

• prepareImageVerification(imagePath): Prepares all inputs needed for proof generation
• hashImageOffCircuit(imageData): Computes complete SHA-256 hash
• hashUntilFinalRound(imageData): Computes SHA-256 up to the final round
• performFinalSHA256Round(...): Executes final SHA-256 round in-circuit
• computeOnChainCommitment(imageData): Computes the exact commitment value stored on-chain (SHA-256 → Poseidon)

How It Works

This zkApp optimizes proof generation by splitting SHA-256 computation:

1. Off-circuit: Computes rounds 0-62 of SHA-256 in JavaScript
2. In-circuit: Only verifies the final round (63) using zkSNARKs

Circuit Analysis

The AuthenticityProgram method verifyAuthenticity has the following summary:

{
  'Total rows': 908,
  Generic: 169,
  EndoMulScalar: 218,
  Rot64: 6,
  RangeCheck0: 18,
  Xor16: 36,
  Zero: 147,
  RangeCheck1: 6,
  ForeignFieldAdd: 3,
  Poseidon: 198,
  CompleteAdd: 5,
  VarBaseMul: 102
}

Development

Build

npm run build

Run Tests

npm run test

Lint & Format

npm run lint
npm run format

Requirements

• Node.js >= 18.14.0
• o1js >= 2.0.0

License

Apache-2.0