erc20 mixer support WIP

.env.example

@@ -3,3 +3,4 @@ MERKLE_TREE_HEIGHT=16
 AMOUNT=1000000000000000000
 EMPTY_ELEMENT=1337
 PRIVATE_KEY=
+ERC20_TOKEN=

contracts/ERC20Mixer.sol

@@ -0,0 +1,53 @@
+// https://tornado.cash
+/*
+* d888888P                                           dP              a88888b.                   dP
+*    88                                              88             d8'   `88                   88
+*    88    .d8888b. 88d888b. 88d888b. .d8888b. .d888b88 .d8888b.    88        .d8888b. .d8888b. 88d888b.
+*    88    88'  `88 88'  `88 88'  `88 88'  `88 88'  `88 88'  `88    88        88'  `88 Y8ooooo. 88'  `88
+*    88    88.  .88 88       88    88 88.  .88 88.  .88 88.  .88 dP Y8.   .88 88.  .88       88 88    88
+*    dP    `88888P' dP       dP    dP `88888P8 `88888P8 `88888P' 88  Y88888P' `88888P8 `88888P' dP    dP
+* ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
+*/
+
+pragma solidity ^0.5.8;
+
+import "./Mixer.sol";
+import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+
+contract ERC20Mixer is Mixer {
+  IERC20 public token;
+
+  constructor(
+    address _verifier,
+    uint256 _transferValue,
+    uint8 _merkleTreeHeight,
+    uint256 _emptyElement,
+    address payable _operator,
+    IERC20 _token
+  ) Mixer(_verifier, _transferValue, _merkleTreeHeight, _emptyElement, _operator) public {
+    token = _token;
+  }
+
+  function deposit(uint256 commitment) public {
+    require(token.transferFrom(msg.sender, address(this), transferValue), "Approve before using");
+    _deposit(commitment);
+
+    emit Deposit(commitment, next_index - 1, block.timestamp);
+  }
+
+  function withdraw(uint256[2] memory a, uint256[2][2] memory b, uint256[2] memory c, uint256[4] memory input) public {
+    _withdraw(a, b, c, input);
+    address receiver = address(input[2]);
+    uint256 fee = input[3];
+    uint256 nullifierHash = input[1];
+
+    require(fee < transferValue, "Fee exceeds transfer value");
+    token.transfer(receiver, transferValue - fee);
+
+    if (fee > 0) {
+      token.transfer(operator, fee);
+    }
+
+    emit Withdraw(receiver, nullifierHash, fee);
+  }
+}

contracts/ETHMixer.sol

@@ -0,0 +1,47 @@
+// https://tornado.cash
+/*
+* d888888P                                           dP              a88888b.                   dP
+*    88                                              88             d8'   `88                   88
+*    88    .d8888b. 88d888b. 88d888b. .d8888b. .d888b88 .d8888b.    88        .d8888b. .d8888b. 88d888b.
+*    88    88'  `88 88'  `88 88'  `88 88'  `88 88'  `88 88'  `88    88        88'  `88 Y8ooooo. 88'  `88
+*    88    88.  .88 88       88    88 88.  .88 88.  .88 88.  .88 dP Y8.   .88 88.  .88       88 88    88
+*    dP    `88888P' dP       dP    dP `88888P8 `88888P8 `88888P' 88  Y88888P' `88888P8 `88888P' dP    dP
+* ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
+*/
+
+pragma solidity ^0.5.8;
+
+import "./Mixer.sol";
+
+contract ETHMixer is Mixer {
+
+  constructor(
+    address _verifier,
+    uint256 _transferValue,
+    uint8 _merkleTreeHeight,
+    uint256 _emptyElement,
+    address payable _operator
+  ) Mixer(_verifier, _transferValue, _merkleTreeHeight, _emptyElement, _operator) public {}
+
+  function deposit(uint256 commitment) public payable {
+    require(msg.value == transferValue, "Please send `transferValue` ETH along with transaction");
+    _deposit(commitment);
+
+    emit Deposit(commitment, next_index - 1, block.timestamp);
+  }
+
+  function withdraw(uint256[2] memory a, uint256[2][2] memory b, uint256[2] memory c, uint256[4] memory input) public {
+    _withdraw(a, b, c, input);
+    address payable receiver = address(input[2]);
+    uint256 fee = input[3];
+    uint256 nullifierHash = input[1];
+
+    require(fee < transferValue, "Fee exceeds transfer value");
+    receiver.transfer(transferValue - fee);
+    if (fee > 0) {
+      operator.transfer(fee);
+    }
+
+    emit Withdraw(receiver, nullifierHash, fee);
+  }
+}

contracts/Mixer.sol

@@ -52,13 +52,11 @@ contract Mixer is MerkleTreeWithHistory {
     @dev Deposit funds into mixer. The caller must send value equal to `transferValue` of this mixer.
     @param commitment the note commitment, which is PedersenHash(nullifier + secret)
   */
-  function deposit(uint256 commitment) public payable {
+  function _deposit(uint256 commitment) internal {
     require(isDepositsEnabled, "deposits disabled");
-    require(msg.value == transferValue, "Please send `transferValue` ETH along with transaction");
     require(!commitments[commitment], "The commitment has been submitted");
     _insert(commitment);
     commitments[commitment] = true;
-    emit Deposit(commitment, next_index - 1, block.timestamp);
   }
 
   /**
@@ -69,23 +67,16 @@ contract Mixer is MerkleTreeWithHistory {
       - the receiver of funds
       - optional fee that goes to the transaction sender (usually a relay)
   */
-  function withdraw(uint256[2] memory a, uint256[2][2] memory b, uint256[2] memory c, uint256[4] memory input) public {
+  function _withdraw(uint256[2] memory a, uint256[2][2] memory b, uint256[2] memory c, uint256[4] memory input) internal {
     uint256 root = input[0];
     uint256 nullifierHash = input[1];
-    address payable receiver = address(input[2]);
-    uint256 fee = input[3];
 
     require(!nullifierHashes[nullifierHash], "The note has been already spent");
-    require(fee < transferValue, "Fee exceeds transfer value");
+
     require(isKnownRoot(root), "Cannot find your merkle root"); // Make sure to use a recent one
     require(verifier.verifyProof(a, b, c, input), "Invalid withdraw proof");
 
     nullifierHashes[nullifierHash] = true;
-    receiver.transfer(transferValue - fee);
-    if (fee > 0) {
-      operator.transfer(fee);
-    }
-    emit Withdraw(receiver, nullifierHash, fee);
   }
 
   function toggleDeposits() external {

contracts/Mocks/ERC20Mock.sol

@@ -0,0 +1,10 @@
+pragma solidity ^0.5.0;
+
+import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+import "@openzeppelin/contracts/token/ERC20/ERC20Mintable.sol";
+import "@openzeppelin/contracts/token/ERC20/ERC20Detailed.sol";
+
+contract ERC20Mock is ERC20Detailed, ERC20Mintable {
+  constructor() ERC20Detailed("DAIMock", "DAIM", 18) public {
+  }
+}

migrations/4_deploy_eth_mixer.js

@@ -1,6 +1,6 @@
 /* global artifacts */
 require('dotenv').config({ path: '../.env' })
-const Mixer = artifacts.require('Mixer')
+const ETHMixer = artifacts.require('ETHMixer')
 const Verifier = artifacts.require('Verifier')
 const MiMC = artifacts.require('MiMC')
 
@@ -10,8 +10,8 @@ module.exports = function(deployer, network, accounts) {
     const { MERKLE_TREE_HEIGHT, AMOUNT, EMPTY_ELEMENT } = process.env
     const verifier = await Verifier.deployed()
     const miMC = await MiMC.deployed()
-    await Mixer.link(MiMC, miMC.address)
-    const mixer = await deployer.deploy(Mixer, verifier.address, AMOUNT, MERKLE_TREE_HEIGHT, EMPTY_ELEMENT, accounts[0])
-    console.log('Mixer\'s address ', mixer.address)
+    await ETHMixer.link(MiMC, miMC.address)
+    const mixer = await deployer.deploy(ETHMixer, verifier.address, AMOUNT, MERKLE_TREE_HEIGHT, EMPTY_ELEMENT, accounts[0])
+    console.log('ETHMixer\'s address ', mixer.address)
   })
 }

migrations/5_deploy_erc20_mixer.js

@@ -0,0 +1,31 @@
+/* global artifacts */
+require('dotenv').config({ path: '../.env' })
+const ERC20Mixer = artifacts.require('ERC20Mixer')
+const Verifier = artifacts.require('Verifier')
+const MiMC = artifacts.require('MiMC')
+const ERC20Mock = artifacts.require('ERC20Mock')
+
+
+module.exports = function(deployer, network, accounts) {
+  return deployer.then(async () => {
+    const { MERKLE_TREE_HEIGHT, AMOUNT, EMPTY_ELEMENT, ERC20_TOKEN } = process.env
+    const verifier = await Verifier.deployed()
+    const miMC = await MiMC.deployed()
+    await ERC20Mixer.link(MiMC, miMC.address)
+    let token = ERC20_TOKEN
+    if(deployer.network !== 'mainnet') {
+      const tokenInstance = await deployer.deploy(ERC20Mock)
+      token = tokenInstance.address
+    }
+    const mixer = await deployer.deploy(
+      ERC20Mixer,
+      verifier.address,
+      AMOUNT,
+      MERKLE_TREE_HEIGHT,
+      EMPTY_ELEMENT,
+      accounts[0],
+      token
+    )
+    console.log('ERC20Mixer\'s address ', mixer.address)
+  })
+}

package-lock.json

@@ -30,6 +30,11 @@
         "regenerator-runtime": "^0.13.2"
       }
     },
+    "@openzeppelin/contracts": {
+      "version": "2.3.0",
+      "resolved": "https://registry.npmjs.org/@openzeppelin/contracts/-/contracts-2.3.0.tgz",
+      "integrity": "sha512-lf8C3oULQAnsu3OTRP4tP5/ddfil6l65Lg3JQCwAIgc99vZ1jz5qeBoETGGGmczxt+bIyMI06WPP2apC74EZag=="
+    },
     "@resolver-engine/core": {
       "version": "0.2.1",
       "resolved": "https://registry.npmjs.org/@resolver-engine/core/-/core-0.2.1.tgz",

package.json

@@ -22,6 +22,7 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
+    "@openzeppelin/contracts": "^2.3.0",
     "bn-chai": "^1.0.1",
     "browserify": "^16.3.0",
     "chai": "^4.2.0",

test/ERC20Mixer.test.js

@@ -0,0 +1,126 @@
+/* global artifacts, web3, contract */
+require('chai')
+  .use(require('bn-chai')(web3.utils.BN))
+  .use(require('chai-as-promised'))
+  .should()
+const fs = require('fs')
+
+const { toBN, toHex, randomHex } = require('web3-utils')
+const { takeSnapshot, revertSnapshot } = require('../lib/ganacheHelper')
+
+const Mixer = artifacts.require('./ERC20Mixer.sol')
+const Token = artifacts.require('./ERC20Mock.sol')
+const { AMOUNT, MERKLE_TREE_HEIGHT, EMPTY_ELEMENT } = process.env
+
+const websnarkUtils = require('websnark/src/utils')
+const buildGroth16 = require('websnark/src/groth16')
+const stringifyBigInts = require('websnark/tools/stringifybigint').stringifyBigInts
+const unstringifyBigInts2 = require('snarkjs/src/stringifybigint').unstringifyBigInts
+const snarkjs = require('snarkjs')
+const bigInt = snarkjs.bigInt
+const crypto = require('crypto')
+const circomlib = require('circomlib')
+const MerkleTree = require('../lib/MerkleTree')
+
+const rbigint = (nbytes) => snarkjs.bigInt.leBuff2int(crypto.randomBytes(nbytes))
+const pedersenHash = (data) => circomlib.babyJub.unpackPoint(circomlib.pedersenHash.hash(data))[0]
+
+function generateDeposit() {
+  let deposit = {
+    secret: rbigint(31),
+    nullifier: rbigint(31),
+  }
+  const preimage = Buffer.concat([deposit.nullifier.leInt2Buff(31), deposit.secret.leInt2Buff(31)])
+  deposit.commitment = pedersenHash(preimage)
+  return deposit
+}
+
+// eslint-disable-next-line no-unused-vars
+function BNArrayToStringArray(array) {
+  const arrayToPrint = []
+  array.forEach(item => {
+    arrayToPrint.push(item.toString())
+  })
+  return arrayToPrint
+}
+
+function getRandomReceiver() {
+  let receiver = rbigint(20)
+  while (toHex(receiver.toString()).length !== 42) {
+    receiver = rbigint(20)
+  }
+  return receiver
+}
+
+function snarkVerify(proof) {
+  proof = unstringifyBigInts2(websnarkUtils.fromSolidityInput(proof))
+  const verification_key = unstringifyBigInts2(require('../build/circuits/withdraw_verification_key.json'))
+  return snarkjs['groth'].isValid(verification_key, proof, proof.publicSignals)
+}
+
+contract('Mixer', accounts => {
+  let mixer
+  let token
+  const sender = accounts[0]
+  const operator = accounts[0]
+  const levels = MERKLE_TREE_HEIGHT || 16
+  const zeroValue = EMPTY_ELEMENT || 1337
+  const value = AMOUNT || '1000000000000000000' // 1 ether
+  let snapshotId
+  let prefix = 'test'
+  let tree
+  const fee = bigInt(AMOUNT).shr(1) || bigInt(1e17)
+  const receiver = getRandomReceiver()
+  const relayer = accounts[1]
+  let groth16
+  let circuit
+  let proving_key
+
+  before(async () => {
+    tree = new MerkleTree(
+      levels,
+      zeroValue,
+      null,
+      prefix,
+    )
+    mixer = await Mixer.deployed()
+    token = await Token.deployed()
+    token.mint(sender, value)
+    snapshotId = await takeSnapshot()
+    groth16 = await buildGroth16()
+    circuit = require('../build/circuits/withdraw.json')
+    proving_key = fs.readFileSync('build/circuits/withdraw_proving_key.bin').buffer
+  })
+
+  describe('#constructor', () => {
+    it('should initialize', async () => {
+      const tokenFromContract = await mixer.token()
+      tokenFromContract.should.be.equal(token.address)
+    })
+  })
+
+  describe('#deposit', () => {
+    it.only('should work', async () => {
+      const commitment = 43
+      await token.approve(mixer.address, value)
+
+      let { logs } = await mixer.deposit(commitment, { from: sender })
+
+      logs[0].event.should.be.equal('Deposit')
+      logs[0].args.commitment.should.be.eq.BN(toBN(commitment))
+      logs[0].args.leafIndex.should.be.eq.BN(toBN(0))
+    })
+  })
+
+  afterEach(async () => {
+    await revertSnapshot(snapshotId.result)
+    // eslint-disable-next-line require-atomic-updates
+    snapshotId = await takeSnapshot()
+    tree = new MerkleTree(
+      levels,
+      zeroValue,
+      null,
+      prefix,
+    )
+  })
+})

test/ETHMixer.test.js

@@ -8,7 +8,7 @@ const fs = require('fs')
 const { toBN, toHex, randomHex } = require('web3-utils')
 const { takeSnapshot, revertSnapshot } = require('../lib/ganacheHelper')
 
-const Mixer = artifacts.require('./Mixer.sol')
+const Mixer = artifacts.require('./ETHMixer.sol')
 const { AMOUNT, MERKLE_TREE_HEIGHT, EMPTY_ELEMENT } = process.env
 
 const websnarkUtils = require('websnark/src/utils')