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README.txt

CIRCOM ZKP SEMAPHORE WORKSPACE

Welcome to the Remix Circom ZKP Hash Checker Workspace. 

The workspace comprises two main directories:

- circuits: Contains sample hash checker circuit. These can be compiled to generate a witness using 'Circom ZKP Compiler' plugin.
- scripts: Provides a sample script designed for a trusted setup using snarkjs. This script also aids 
in generating Solidity code, which is essential for on-chain deployment.

circuits...calculate_hash.circom

pragma circom 2.0.0;

include "circomlib/poseidon.circom";

template CalculateHash() {
    signal input value1;
    signal input value2;
    signal input value3;
    signal input value4;
    signal output out;

    component poseidon = Poseidon(4);

    poseidon.inputs[0] <== value1;
    poseidon.inputs[1] <== value2;
    poseidon.inputs[2] <== value3;
    poseidon.inputs[3] <== value4;

    out <== poseidon.out;
}
template HashChecker() {
    signal input value1;
    signal input value2;
    signal input value3;
    signal input value4;
    signal input hash;

    component calculateSecret = CalculateHash();
    calculateSecret.value1 <== value1;
    calculateSecret.value2 <== value2;
    calculateSecret.value3 <== value3;
    calculateSecret.value4 <== value4;

    signal calculatedHash;
    calculatedHash <== calculateSecret.out;

    assert(hash == calculatedHash);
    
}

component main {public [value1, value2, value3, value4]} = HashChecker();

scripts...run_setup.ts

import { ethers, BigNumber } from 'ethers'

// eslint-disable-next-line @typescript-eslint/no-var-requires
const snarkjs = require('snarkjs');

const logger = {
  info: (...args) => console.log(...args),
  debug: (...args) => console.log(...args)
};

/**
 * Creates a keccak256 hash of a message compatible with the SNARK scalar modulus.
 * @param message The message to be hashed.
 * @returns The message digest.
 */
function hash(message: any): bigint {
  message = BigNumber.from(message).toTwos(256).toHexString()
  message = ethers.utils.zeroPad(message, 32)
  return BigInt(ethers.utils.keccak256(message)) >> BigInt(8)
}

(async () => {
  try {
    // @ts-ignore
    await remix.call('circuit-compiler', 'generateR1cs', 'circuits/calculate_hash.circom');

    const ptau_final = "https://ipfs-cluster.ethdevops.io/ipfs/QmTiT4eiYz5KF7gQrDsgfCSTRv3wBPYJ4bRN1MmTRshpnW";
    // @ts-ignore
    const r1csBuffer = await remix.call('fileManager', 'readFile', 'circuits/.bin/calculate_hash.r1cs', true);
    // @ts-ignore
    const r1cs = new Uint8Array(r1csBuffer);
    const zkey_0 = { type: "mem" };
    const zkey_1 = { type: "mem" };
    const zkey_final = { type: "mem" };

    console.log('newZkey')
    await snarkjs.zKey.newZKey(r1cs, ptau_final, zkey_0);

    console.log('contribute')
    await snarkjs.zKey.contribute(zkey_0, zkey_1, "p2_C1", "pa_Entropy1");

    console.log('beacon')
    await snarkjs.zKey.beacon(zkey_1, zkey_final, "B3", "0102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f20", 10);

    console.log('verifyFromR1cs')
    const verifyFromR1csResult = await snarkjs.zKey.verifyFromR1cs(r1cs, ptau_final, zkey_final);
    console.assert(verifyFromR1csResult);

    console.log('verifyFromInit')
    const verifyFromInit = await snarkjs.zKey.verifyFromInit(zkey_0, ptau_final, zkey_final);
    console.assert(verifyFromInit);

    console.log('exportVerificationKey')
    const vKey = await snarkjs.zKey.exportVerificationKey(zkey_final)
    await remix.call('fileManager', 'writeFile', './zk/build/verification_key.json', JSON.stringify(vKey))
    
    const templates = {
      groth16: await remix.call('fileManager', 'readFile', 'templates/groth16_verifier.sol.ejs')
    }
    const solidityContract = await snarkjs.zKey.exportSolidityVerifier(zkey_final, templates)
    
    await remix.call('fileManager', 'writeFile', './zk/build/zk_verifier.sol', solidityContract)
    
    console.log('buffer', (zkey_final as any).data.length)
    await remix.call('fileManager', 'writeFile', './zk/build/zk_setup.txt', JSON.stringify(Array.from(((zkey_final as any).data))))
    
    console.log('setup done.')
    
  } catch (e) {
    console.error(e.message)
  }
})()

scripts...run_verification.ts

import { poseidon } from "circomlibjs" // v0.0.8

// eslint-disable-next-line @typescript-eslint/no-var-requires
const snarkjs = require('snarkjs');

const logger = {
  info: (...args) => console.log(...args),
  debug: (...args) => console.log(...args),
  error: (...args) => console.error(...args),
}

/**
 * Creates a keccak256 hash of a message compatible with the SNARK scalar modulus.
 * @param message The message to be hashed.
 * @returns The message digest.
 */
function hash(message: any): bigint {
  message = BigNumber.from(message).toTwos(256).toHexString()
  message = ethers.utils.zeroPad(message, 32)
  return BigInt(ethers.utils.keccak256(message)) >> BigInt(8)
}

(async () => {
  try {
    // @ts-ignore
    const r1csBuffer = await remix.call('fileManager', 'readFile', 'circuits/.bin/calculate_hash.r1cs', true);
    // @ts-ignore
    const r1cs = new Uint8Array(r1csBuffer);
    // @ts-ignore
    const wasmBuffer = await remix.call('fileManager', 'readFile', 'circuits/.bin/calculate_hash.wasm', true);
    // @ts-ignore
    const wasm = new Uint8Array(wasmBuffer);   
     
    const zkey_final = {
      type: "mem",
      data: new Uint8Array(JSON.parse(await remix.call('fileManager', 'readFile', './zk/build/zk_setup.txt')))
    }
    const wtns = { type: "mem" };   

    const vKey = JSON.parse(await remix.call('fileManager', 'readFile', './zk/build/verification_key.json'))
  
    const value1 = '1234'
    const value2 = '2'
    const value3 = '3'
    const value4 = '4'
    
    const wrongValue = '5' // put this in the poseidon hash calculation to simulate a non matching hash.

    const signals = {
      value1,
      value2,
      value3,
      value4,
      hash: poseidon([value1, value2, value3, value4])
    }
    
    console.log('calculate')
    await snarkjs.wtns.calculate(signals, wasm, wtns);
    
    console.log('check')
    await snarkjs.wtns.check(r1cs, wtns, logger);
    

    console.log('prove')
    const { proof, publicSignals } = await snarkjs.groth16.prove(zkey_final, wtns);
    
    const verified = await snarkjs.groth16.verify(vKey, publicSignals, proof, logger);
    console.log('zk proof validity', verified);
    
    
  } catch (e) {
    console.error(e.message)
  }
})()

templates...groth16_verifier.sol.ejs

// SPDX-License-Identifier: GPL-3.0
/*
    Copyright 2021 0KIMS association.

    This file is generated with [snarkJS](https://github.com/iden3/snarkjs).

    snarkJS is a free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    snarkJS is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
    License for more details.

    You should have received a copy of the GNU General Public License
    along with snarkJS. If not, see <https://www.gnu.org/licenses/>.
*/

pragma solidity >=0.7.0 <0.9.0;

contract Groth16Verifier {
    // Scalar field size
    uint256 constant r    = 21888242871839275222246405745257275088548364400416034343698204186575808495617;
    // Base field size
    uint256 constant q   = 21888242871839275222246405745257275088696311157297823662689037894645226208583;

    // Verification Key data
    uint256 constant alphax  = <%= vk_alpha_1[0]    %>;
    uint256 constant alphay  = <%= vk_alpha_1[1]    %>;
    uint256 constant betax1  = <%= vk_beta_2[0][1]  %>;
    uint256 constant betax2  = <%= vk_beta_2[0][0]  %>;
    uint256 constant betay1  = <%= vk_beta_2[1][1]  %>;
    uint256 constant betay2  = <%= vk_beta_2[1][0]  %>;
    uint256 constant gammax1 = <%= vk_gamma_2[0][1] %>;
    uint256 constant gammax2 = <%= vk_gamma_2[0][0] %>;
    uint256 constant gammay1 = <%= vk_gamma_2[1][1] %>;
    uint256 constant gammay2 = <%= vk_gamma_2[1][0] %>;
    uint256 constant deltax1 = <%= vk_delta_2[0][1] %>;
    uint256 constant deltax2 = <%= vk_delta_2[0][0] %>;
    uint256 constant deltay1 = <%= vk_delta_2[1][1] %>;
    uint256 constant deltay2 = <%= vk_delta_2[1][0] %>;

    <% for (let i=0; i<IC.length; i++) { %>
    uint256 constant IC<%=i%>x = <%=IC[i][0]%>;
    uint256 constant IC<%=i%>y = <%=IC[i][1]%>;
    <% } %>
 
    // Memory data
    uint16 constant pVk = 0;
    uint16 constant pPairing = 128;

    uint16 constant pLastMem = 896;

    function verifyProof(uint[2] calldata _pA, uint[2][2] calldata _pB, uint[2] calldata _pC, uint[<%=IC.length-1%>] calldata _pubSignals) public view returns (bool) {
        assembly {
            function checkField(v) {
                if iszero(lt(v, q)) {
                    mstore(0, 0)
                    return(0, 0x20)
                }
            }
            
            // G1 function to multiply a G1 value(x,y) to value in an address
            function g1_mulAccC(pR, x, y, s) {
                let success
                let mIn := mload(0x40)
                mstore(mIn, x)
                mstore(add(mIn, 32), y)
                mstore(add(mIn, 64), s)

                success := staticcall(sub(gas(), 2000), 7, mIn, 96, mIn, 64)

                if iszero(success) {
                    mstore(0, 0)
                    return(0, 0x20)
                }

                mstore(add(mIn, 64), mload(pR))
                mstore(add(mIn, 96), mload(add(pR, 32)))

                success := staticcall(sub(gas(), 2000), 6, mIn, 128, pR, 64)

                if iszero(success) {
                    mstore(0, 0)
                    return(0, 0x20)
                }
            }

            function checkPairing(pA, pB, pC, pubSignals, pMem) -> isOk {
                let _pPairing := add(pMem, pPairing)
                let _pVk := add(pMem, pVk)

                mstore(_pVk, IC0x)
                mstore(add(_pVk, 32), IC0y)

                // Compute the linear combination vk_x
                <% for (let i = 1; i <= nPublic; i++) { %>
                g1_mulAccC(_pVk, IC<%=i%>x, IC<%=i%>y, calldataload(add(pubSignals, <%=(i-1)*32%>)))
                <% } %>

                // -A
                mstore(_pPairing, calldataload(pA))
                mstore(add(_pPairing, 32), mod(sub(q, calldataload(add(pA, 32))), q))

                // B
                mstore(add(_pPairing, 64), calldataload(pB))
                mstore(add(_pPairing, 96), calldataload(add(pB, 32)))
                mstore(add(_pPairing, 128), calldataload(add(pB, 64)))
                mstore(add(_pPairing, 160), calldataload(add(pB, 96)))

                // alpha1
                mstore(add(_pPairing, 192), alphax)
                mstore(add(_pPairing, 224), alphay)

                // beta2
                mstore(add(_pPairing, 256), betax1)
                mstore(add(_pPairing, 288), betax2)
                mstore(add(_pPairing, 320), betay1)
                mstore(add(_pPairing, 352), betay2)

                // vk_x
                mstore(add(_pPairing, 384), mload(add(pMem, pVk)))
                mstore(add(_pPairing, 416), mload(add(pMem, add(pVk, 32))))


                // gamma2
                mstore(add(_pPairing, 448), gammax1)
                mstore(add(_pPairing, 480), gammax2)
                mstore(add(_pPairing, 512), gammay1)
                mstore(add(_pPairing, 544), gammay2)

                // C
                mstore(add(_pPairing, 576), calldataload(pC))
                mstore(add(_pPairing, 608), calldataload(add(pC, 32)))

                // delta2
                mstore(add(_pPairing, 640), deltax1)
                mstore(add(_pPairing, 672), deltax2)
                mstore(add(_pPairing, 704), deltay1)
                mstore(add(_pPairing, 736), deltay2)


                let success := staticcall(sub(gas(), 2000), 8, _pPairing, 768, _pPairing, 0x20)

                isOk := and(success, mload(_pPairing))
            }

            let pMem := mload(0x40)
            mstore(0x40, add(pMem, pLastMem))

            // Validate that all evaluations ∈ F
            <% for (let i=0; i<IC.length; i++) { %>
            checkField(calldataload(add(_pubSignals, <%=i*32%>)))
            <% } %>

            // Validate all evaluations
            let isValid := checkPairing(_pA, _pB, _pC, _pubSignals, pMem)

            mstore(0, isValid)
             return(0, 0x20)
         }
     }
 }