remove mimc and snarkjs dependency

package.json

@@ -1,6 +1,6 @@
 {
   "name": "fixed-merkle-tree",
-  "version": "0.6.0",
+  "version": "1.0.0",
   "description": "Fixed depth merkle tree implementation with sequential inserts",
   "repository": "https://github.com/tornadocash/fixed-merkle-tree.git",
   "main": "src/merkleTree.js",
@@ -18,10 +18,6 @@
   "files": [
     "src/*"
   ],
-  "dependencies": {
-    "snarkjs": "git+https://github.com/tornadocash/snarkjs.git#869181cfaf7526fe8972073d31655493a04326d5",
-    "circomlib": "git+https://github.com/tornadocash/circomlib.git#5beb6aee94923052faeecea40135d45b6ce6172c"
-  },
   "devDependencies": {
     "babel-eslint": "^10.1.0",
     "chai": "^4.2.0",

src/merkleTree.js

@@ -1,9 +1,5 @@
-// keccak256("tornado") % BN254_FIELD_SIZE
-const DEFAULT_ZERO = '21663839004416932945382355908790599225266501822907911457504978515578255421292'
-const defaultHash = require('./mimc')
-
+const defaultHash = require('./sha256')
 // todo ensure consistent types in tree and inserted elements?
-// todo make sha3 default hasher (and update tests) to get rid of mimc/snarkjs/circomlib dependency
 
 /**
  * @callback hashFunction
@@ -22,7 +18,7 @@ class MerkleTree {
    * @param {hashFunction} [options.hashFunction] Function used to hash 2 leaves
    * @param [options.zeroElement] Value for non-existent leaves
    */
-  constructor(levels, elements = [], { hashFunction, zeroElement = DEFAULT_ZERO } = {}) {
+  constructor(levels, elements = [], { hashFunction, zeroElement = 0 } = {}) {
     this.levels = levels
     this.capacity = 2 ** levels
     if (elements.length > this.capacity) {

src/mimc.js

@@ -1,3 +0,0 @@
-const { mimcsponge } = require('circomlib')
-const { bigInt } = require('snarkjs')
-module.exports = (left, right) => mimcsponge.multiHash([bigInt(left), bigInt(right)]).toString()

src/sha256.js

@@ -0,0 +1,15 @@
+const crypto = require('crypto')
+
+function toBuffer256(number) {
+  return Buffer.from(number.toString(16).padStart(512, '0'), 'hex')
+}
+
+function sha256(left, right) {
+  return crypto
+    .createHash('sha256')
+    .update(toBuffer256(left))
+    .update(toBuffer256(right))
+    .digest('hex')
+}
+
+module.exports = sha256