changed emptyElement to constant

.env.example

@@ -2,7 +2,6 @@ MERKLE_TREE_HEIGHT=16
 # in wei
 ETH_AMOUNT=100000000000000000
 TOKEN_AMOUNT=100000000000000000
-EMPTY_ELEMENT=1
 PRIVATE_KEY=
 ERC20_TOKEN=
 

cli.js

@@ -13,7 +13,7 @@ const buildGroth16 = require('websnark/src/groth16')
 const websnarkUtils = require('websnark/src/utils')
 
 let web3, mixer, erc20mixer, circuit, proving_key, groth16, erc20
-let MERKLE_TREE_HEIGHT, ETH_AMOUNT, EMPTY_ELEMENT, ERC20_TOKEN
+let MERKLE_TREE_HEIGHT, ETH_AMOUNT, ERC20_TOKEN
 const inBrowser = (typeof window !== 'undefined')
 
 /** Generate random number of specified byte length */
@@ -83,7 +83,7 @@ async function withdrawErc20(note, receiver, relayer) {
       }
       return e.returnValues.commitment
     })
-  const tree = new merkleTree(MERKLE_TREE_HEIGHT, EMPTY_ELEMENT, leaves)
+  const tree = new merkleTree(MERKLE_TREE_HEIGHT, leaves)
   const validRoot = await erc20mixer.methods.isKnownRoot(await tree.root()).call()
   const nullifierHash = pedersenHash(deposit.nullifier.leInt2Buff(31))
   const nullifierHashToCheck = nullifierHash.toString(16).padStart('66', '0x000000')
@@ -152,7 +152,7 @@ async function withdraw(note, receiver) {
   const leaves = events
     .sort((a, b) => a.returnValues.leafIndex.sub(b.returnValues.leafIndex)) // Sort events in chronological order
     .map(e => e.returnValues.commitment)
-  const tree = new merkleTree(MERKLE_TREE_HEIGHT, EMPTY_ELEMENT, leaves)
+  const tree = new merkleTree(MERKLE_TREE_HEIGHT, leaves)
 
   // Find current commitment in the tree
   let depositEvent = events.find(e => e.returnValues.commitment.eq(paddedCommitment))
@@ -210,7 +210,6 @@ async function init() {
     proving_key = await (await fetch('build/circuits/withdraw_proving_key.bin')).arrayBuffer()
     MERKLE_TREE_HEIGHT = 16
     ETH_AMOUNT = 1e18
-    EMPTY_ELEMENT = 1
   } else {
     // Initialize from local node
     web3 = new Web3('http://localhost:8545', null, { transactionConfirmationBlocks: 1 })
@@ -220,7 +219,6 @@ async function init() {
     require('dotenv').config()
     MERKLE_TREE_HEIGHT = process.env.MERKLE_TREE_HEIGHT
     ETH_AMOUNT = process.env.ETH_AMOUNT
-    EMPTY_ELEMENT = process.env.EMPTY_ELEMENT
     ERC20_TOKEN = process.env.ERC20_TOKEN
     erc20ContractJson = require('./build/contracts/ERC20Mock.json')
     erc20mixerJson = require('./build/contracts/ERC20Mixer.json')

contracts/ERC20Mixer.sol

@@ -20,10 +20,9 @@ contract ERC20Mixer is Mixer {
     IVerifier _verifier,
     uint256 _denomination,
     uint8 _merkleTreeHeight,
-    uint256 _emptyElement,
     address _operator,
     address _token
-  ) Mixer(_verifier, _denomination, _merkleTreeHeight, _emptyElement, _operator) public {
+  ) Mixer(_verifier, _denomination, _merkleTreeHeight, _operator) public {
     token = _token;
   }
 

contracts/ETHMixer.sol

@@ -18,9 +18,8 @@ contract ETHMixer is Mixer {
     IVerifier _verifier,
     uint256 _denomination,
     uint8 _merkleTreeHeight,
-    uint256 _emptyElement,
     address _operator
-  ) Mixer(_verifier, _denomination, _merkleTreeHeight, _emptyElement, _operator) public {
+  ) Mixer(_verifier, _denomination, _merkleTreeHeight, _operator) public {
   }
 
   function _processWithdraw(address payable _receiver, address payable _relayer, uint256 _fee, uint256 _refund) internal {

contracts/MerkleTreeWithHistory.sol

@@ -18,8 +18,9 @@ library Hasher {
 contract MerkleTreeWithHistory {
   uint256 public levels;
 
-  uint256 constant FIELD_SIZE = 21888242871839275222246405745257275088548364400416034343698204186575808495617;
+  uint256 public constant FIELD_SIZE = 21888242871839275222246405745257275088548364400416034343698204186575808495617;
-  uint256 constant ROOT_HISTORY_SIZE = 100;
+  uint256 public constant ZERO_VALUE = 5702960885942360421128284892092891246826997279710054143430547229469817701242; // = MiMC("tornado")
+  uint256 public constant ROOT_HISTORY_SIZE = 100;
   uint256[ROOT_HISTORY_SIZE] public _roots;
   uint256 public current_root_index = 0;
 
@@ -28,12 +29,12 @@ contract MerkleTreeWithHistory {
 
   uint32 public next_index = 0;
 
-  constructor(uint256 tree_levels, uint256 zero_value) public {
+  constructor(uint256 tree_levels) public {
     require(tree_levels > 0, "tree_levels should be greater than zero");
     levels = tree_levels;
 
-    uint256 current_zero = zero_value;
+    uint256 current_zero = ZERO_VALUE;
-    _zeros.push(zero_value);
+    _zeros.push(ZERO_VALUE);
     _filled_subtrees.push(current_zero);
 
     for (uint8 i = 1; i < levels; i++) {

contracts/Mixer.sol

@@ -43,16 +43,14 @@ contract Mixer is MerkleTreeWithHistory {
     @dev The constructor
     @param _verifier the address of SNARK verifier for this contract
     @param _merkleTreeHeight the height of deposits' Merkle Tree
-    @param _emptyElement default element of the deposits' Merkle Tree
     @param _operator operator address (see operator above)
   */
   constructor(
     IVerifier _verifier,
     uint256 _denomination,
     uint8 _merkleTreeHeight,
-    uint256 _emptyElement,
     address _operator
-  ) MerkleTreeWithHistory(_merkleTreeHeight, _emptyElement) public {
+  ) MerkleTreeWithHistory(_merkleTreeHeight) public {
     require(_denomination > 0, "denomination should be greater than 0");
     verifier = _verifier;
     operator = _operator;

contracts/Mocks/MerkleTreeWithHistoryMock.sol

@@ -4,7 +4,7 @@ import '../MerkleTreeWithHistory.sol';
 
 contract MerkleTreeWithHistoryMock is MerkleTreeWithHistory {
 
-  constructor (uint8 tree_levels, uint256 zero_value) MerkleTreeWithHistory(tree_levels, zero_value) public {}
+  constructor (uint8 tree_levels) MerkleTreeWithHistory(tree_levels) public {}
 
   function insert(uint256 leaf) public {
       _insert(leaf);

lib/MerkleTree.js

@@ -1,9 +1,10 @@
 const jsStorage = require('./Storage')
 const hasherImpl = require('./MiMC')
+const { bigInt } = require('snarkjs')
 
 class MerkleTree {
 
-  constructor(n_levels, zero_value, defaultElements, prefix, storage, hasher) {
+  constructor(n_levels, defaultElements, prefix, storage, hasher) {
     this.prefix = prefix
     this.storage = storage || new jsStorage()
     this.hasher = hasher || new hasherImpl()
@@ -11,7 +12,7 @@ class MerkleTree {
     this.zero_values = []
     this.totalElements = 0
 
-    let current_zero_value = zero_value || 0
+    let current_zero_value = bigInt('5702960885942360421128284892092891246826997279710054143430547229469817701242')
     this.zero_values.push(current_zero_value)
     for (let i = 0; i < n_levels; i++) {
       current_zero_value = this.hasher.hash(i, current_zero_value, current_zero_value)

migrations/4_deploy_eth_mixer.js

@@ -7,11 +7,11 @@ const hasherContract = artifacts.require('Hasher')
 
 module.exports = function(deployer, network, accounts) {
   return deployer.then(async () => {
-    const { MERKLE_TREE_HEIGHT, ETH_AMOUNT, EMPTY_ELEMENT } = process.env
+    const { MERKLE_TREE_HEIGHT, ETH_AMOUNT } = process.env
     const verifier = await Verifier.deployed()
     const hasherInstance = await hasherContract.deployed()
     await ETHMixer.link(hasherContract, hasherInstance.address)
-    const mixer = await deployer.deploy(ETHMixer, verifier.address, ETH_AMOUNT, MERKLE_TREE_HEIGHT, EMPTY_ELEMENT, accounts[0])
+    const mixer = await deployer.deploy(ETHMixer, verifier.address, ETH_AMOUNT, MERKLE_TREE_HEIGHT, accounts[0])
     console.log('ETHMixer\'s address ', mixer.address)
   })
 }

migrations/5_deploy_erc20_mixer.js

@@ -8,7 +8,7 @@ const ERC20Mock = artifacts.require('ERC20Mock')
 
 module.exports = function(deployer, network, accounts) {
   return deployer.then(async () => {
-    const { MERKLE_TREE_HEIGHT, EMPTY_ELEMENT, ERC20_TOKEN, TOKEN_AMOUNT } = process.env
+    const { MERKLE_TREE_HEIGHT, ERC20_TOKEN, TOKEN_AMOUNT } = process.env
     const verifier = await Verifier.deployed()
     const hasherInstance = await hasherContract.deployed()
     await ERC20Mixer.link(hasherContract, hasherInstance.address)
@@ -22,7 +22,6 @@ module.exports = function(deployer, network, accounts) {
       verifier.address,
       TOKEN_AMOUNT,
       MERKLE_TREE_HEIGHT,
-      EMPTY_ELEMENT,
       accounts[0],
       token,
     )

test/ERC20Mixer.test.js

@@ -11,7 +11,7 @@ const { takeSnapshot, revertSnapshot } = require('../lib/ganacheHelper')
 const Mixer = artifacts.require('./ERC20Mixer.sol')
 const Token = artifacts.require('./ERC20Mock.sol')
 const USDTToken = artifacts.require('./IUSDT.sol')
-const { ETH_AMOUNT, TOKEN_AMOUNT, MERKLE_TREE_HEIGHT, EMPTY_ELEMENT, ERC20_TOKEN } = process.env
+const { ETH_AMOUNT, TOKEN_AMOUNT, MERKLE_TREE_HEIGHT, ERC20_TOKEN } = process.env
 
 const websnarkUtils = require('websnark/src/utils')
 const buildGroth16 = require('websnark/src/groth16')
@@ -50,7 +50,6 @@ contract('ERC20Mixer', accounts => {
   const sender = accounts[0]
   const operator = accounts[0]
   const levels = MERKLE_TREE_HEIGHT || 16
-  const zeroValue = EMPTY_ELEMENT || 1337
   let tokenDenomination = TOKEN_AMOUNT || '1000000000000000000' // 1 ether
   let snapshotId
   let prefix = 'test'
@@ -66,7 +65,6 @@ contract('ERC20Mixer', accounts => {
   before(async () => {
     tree = new MerkleTree(
       levels,
-      zeroValue,
       null,
       prefix,
     )
@@ -401,7 +399,6 @@ contract('ERC20Mixer', accounts => {
     snapshotId = await takeSnapshot()
     tree = new MerkleTree(
       levels,
-      zeroValue,
       null,
       prefix,
     )

test/ETHMixer.test.js

@@ -9,7 +9,7 @@ const { toBN, toHex, randomHex } = require('web3-utils')
 const { takeSnapshot, revertSnapshot } = require('../lib/ganacheHelper')
 
 const Mixer = artifacts.require('./ETHMixer.sol')
-const { ETH_AMOUNT, MERKLE_TREE_HEIGHT, EMPTY_ELEMENT } = process.env
+const { ETH_AMOUNT, MERKLE_TREE_HEIGHT } = process.env
 
 const websnarkUtils = require('websnark/src/utils')
 const buildGroth16 = require('websnark/src/groth16')
@@ -62,7 +62,6 @@ contract('ETHMixer', accounts => {
   const sender = accounts[0]
   const operator = accounts[0]
   const levels = MERKLE_TREE_HEIGHT || 16
-  const zeroValue = EMPTY_ELEMENT || 1337
   const value = ETH_AMOUNT || '1000000000000000000' // 1 ether
   let snapshotId
   let prefix = 'test'
@@ -78,7 +77,6 @@ contract('ETHMixer', accounts => {
   before(async () => {
     tree = new MerkleTree(
       levels,
-      zeroValue,
       null,
       prefix,
     )
@@ -521,7 +519,6 @@ contract('ETHMixer', accounts => {
     snapshotId = await takeSnapshot()
     tree = new MerkleTree(
       levels,
-      zeroValue,
       null,
       prefix,
     )

test/MerkleTreeWithHistory.test.js

@@ -12,7 +12,7 @@ const hasherContract = artifacts.require('./Hasher.sol')
 const MerkleTree = require('../lib/MerkleTree')
 const hasherImpl = require('../lib/MiMC')
 
-const { ETH_AMOUNT, MERKLE_TREE_HEIGHT, EMPTY_ELEMENT } = process.env
+const { ETH_AMOUNT, MERKLE_TREE_HEIGHT } = process.env
 
 // eslint-disable-next-line no-unused-vars
 function BNArrayToStringArray(array) {
@@ -27,7 +27,6 @@ contract('MerkleTreeWithHistory', accounts => {
   let merkleTreeWithHistory
   let hasherInstance
   let levels = MERKLE_TREE_HEIGHT || 16
-  let zeroValue = EMPTY_ELEMENT || 1337
   const sender = accounts[0]
   // eslint-disable-next-line no-unused-vars
   const value = ETH_AMOUNT || '1000000000000000000'
@@ -39,19 +38,19 @@ contract('MerkleTreeWithHistory', accounts => {
   before(async () => {
     tree = new MerkleTree(
       levels,
-      zeroValue,
       null,
       prefix,
     )
     hasherInstance = await hasherContract.deployed()
     await MerkleTreeWithHistory.link(hasherContract, hasherInstance.address)
-    merkleTreeWithHistory = await MerkleTreeWithHistory.new(levels, zeroValue)
+    merkleTreeWithHistory = await MerkleTreeWithHistory.new(levels)
     snapshotId = await takeSnapshot()
   })
 
   describe('#constructor', () => {
     it('should initialize', async () => {
       const filled_subtrees = await merkleTreeWithHistory.filled_subtrees()
+      const zeroValue = await merkleTreeWithHistory.ZERO_VALUE()
       filled_subtrees[0].should.be.eq.BN(zeroValue)
       const zeros = await merkleTreeWithHistory.zeros()
       zeros[0].should.be.eq.BN(zeroValue)
@@ -70,7 +69,6 @@ contract('MerkleTreeWithHistory', accounts => {
       hasher = new hasherImpl()
       tree = new MerkleTree(
         2,
-        zeroValue,
         null,
         prefix,
       )
@@ -91,7 +89,6 @@ contract('MerkleTreeWithHistory', accounts => {
 
       const batchTree = new MerkleTree(
         levels,
-        zeroValue,
         elements,
         prefix,
       )
@@ -131,7 +128,6 @@ contract('MerkleTreeWithHistory', accounts => {
 
       const batchTree = new MerkleTree(
         levels,
-        zeroValue,
         elements,
         prefix,
       )
@@ -150,7 +146,6 @@ contract('MerkleTreeWithHistory', accounts => {
       console.time('MerkleTree')
       tree = new MerkleTree(
         levels,
-        zeroValue,
         elements,
         prefix,
       )
@@ -177,8 +172,7 @@ contract('MerkleTreeWithHistory', accounts => {
 
     it('should reject if tree is full', async () => {
       levels = 6
-      zeroValue = 1337
+      merkleTreeWithHistory = await MerkleTreeWithHistory.new(levels)
-      merkleTreeWithHistory = await MerkleTreeWithHistory.new(levels, zeroValue)
 
       for (let i = 0; i < 2**levels; i++) {
         await merkleTreeWithHistory.insert(i+42).should.be.fulfilled
@@ -193,8 +187,8 @@ contract('MerkleTreeWithHistory', accounts => {
 
     it.skip('hasher gas', async () => {
       levels = 6
-      zeroValue = 1337
+      merkleTreeWithHistory = await MerkleTreeWithHistory.new(levels)
-      merkleTreeWithHistory = await MerkleTreeWithHistory.new(levels, zeroValue)
+      const zeroValue = await merkleTreeWithHistory.zeroValue()
 
       const gas = await merkleTreeWithHistory.hashLeftRight.estimateGas(zeroValue, zeroValue)
       console.log('gas', gas - 21000)
@@ -208,7 +202,6 @@ contract('MerkleTreeWithHistory', accounts => {
     hasher = new hasherImpl()
     tree = new MerkleTree(
       levels,
-      zeroValue,
       null,
       prefix,
       null,