feat(@embark/snarks): Allow embark-snark to be used in the dapp

`embark-snark` has been updated such that it can be used, in conjunction with `embarkjs-snark`, in the console, and in the DApp.

This could, for example, be used to build a dapp like https://tornado.cash.

Please see the README for usage instructions.

Updated tests were excluded in this PR as a consideration for time already spent on getting this library completed. Tests should be updated in a future PR.

Author: emizzle

packages/core/code-runner/src/index.ts

@@ -46,6 +46,7 @@ class CodeRunner {
   private whitelistVar(varName: string, cb = () => { }) {
     // @ts-ignore
     this.vm._options.require.external.push(varName); // @ts-ignore
+    cb();
   }
 
   private registerVar(varName: string, code: any, cb = () => { }) {

packages/core/core/src/index.ts

@@ -10,6 +10,7 @@ export interface Contract {
   deployedAddress: string;
   className: string;
   silent?: boolean;
+  methods: any;
 }
 
 export interface ContractConfig {
@@ -100,6 +101,8 @@ export interface Configuration {
   };
   plugins: EmbarkPlugins;
   reloadConfig(): void;
+
+  dappPath(...args: string[]): string;
 }
 
 type ActionCallback<T> = (params: any, cb: Callback<T>) => void;
@@ -108,6 +111,7 @@ import { Logger } from 'embark-logger';
 
 export interface Embark {
   env: string;
+  pluginConfig: any;
   events: EmbarkEvents;
   plugins: EmbarkPlugins;
   registerAPICall(method: string, endpoint: string, cb: (...args: any[]) => void): void;
@@ -118,7 +122,7 @@ export interface Embark {
   currentContext: string[];
   registerActionForEvent<T>(
     name: string,
-    options?: ActionCallback<T> | { priority: number },
+    options?: ActionCallback<T> | { priority: number; },
     action?: ActionCallback<T>,
   ): void;
 }

packages/embarkjs/snark/.babelrc.js

@@ -0,0 +1,31 @@
+/* global module require */
+
+const cloneDeep = require('lodash.clonedeep');
+
+module.exports = (api) => {
+  const env = api.env();
+
+  const base = {};
+
+  const browser = cloneDeep(base);
+  Object.assign(browser, {
+    ignore: [
+      'src/node'
+    ]
+  });
+
+  const node = cloneDeep(base);
+
+  const test = cloneDeep(node);
+
+  switch (env) {
+    case 'browser':
+      return browser;
+    case 'node':
+      return node;
+    case 'test':
+      return test;
+    default:
+      return base;
+  }
+};

packages/embarkjs/snark/.gitignore

@@ -0,0 +1 @@
+build-test

packages/embarkjs/snark/.npmrc

@@ -0,0 +1,4 @@
+engine-strict = true
+package-lock = false
+save-exact = true
+scripts-prepend-node-path = true

packages/embarkjs/snark/README.md

@@ -0,0 +1,8 @@
+# `embarkjs-snark`
+
+> zkSnarks plugin for embarkjs
+
+Exposes functions for interaction with zkSNARKS. See [`embark-snark` README](../../plugins/snark/README.md) for more information.
+
+Visit [embark.status.im](https://embark.status.im/) to get started with
+[Embark](https://github.com/embark-framework/embark).

packages/embarkjs/snark/package.json

@@ -0,0 +1,84 @@
+{
+  "name": "embarkjs-snark",
+  "version": "5.1.1-nightly.2",
+  "author": "Iuri Matias <iuri.matias@gmail.com>",
+  "contributors": [
+    "Eric Mastro <eric.mastro@gmail.com> (https://github.com/emizzle/)"
+  ],
+  "description": "zkSnarks plugin for embarkjs",
+  "homepage": "https://github.com/embark-framework/embark/tree/master/packages/embarkjs/snark#readme",
+  "bugs": "https://github.com/embark-framework/embark/issues",
+  "keywords": [
+    "blockchain",
+    "dapps",
+    "ethereum",
+    "zksnarks",
+    "snarks",
+    "zero knowledge"
+  ],
+  "license": "MIT",
+  "repository": {
+    "directory": "packages/embarkjs/snark",
+    "type": "git",
+    "url": "https://github.com/embark-framework/embark.git"
+  },
+  "main": "./dist/node/index.js",
+  "types": "./dist/index.d.ts",
+  "browser": {
+    "./dist/node/index.js": "./dist/browser/index.js",
+    "./dist/browser/embarkjs-snark.js": "./dist/browser/browser/embarkjs-snark.js"
+  },
+  "browserslist": [
+    "last 1 version",
+    "not dead",
+    "> 0.2%"
+  ],
+  "files": [
+    "dist"
+  ],
+  "embark-collective": {
+    "build:browser": true,
+    "build:node": true,
+    "typecheck": {
+      "compilerOptions": {
+        "module": "ESNext"
+      }
+    }
+  },
+  "scripts": {
+    "_build": "npm run solo -- build",
+    "_typecheck": "npm run solo -- typecheck",
+    "ci": "npm run qa",
+    "clean": "npm run reset",
+    "lint": "npm-run-all lint:*",
+    "// lint:js": "eslint test/",
+    "lint:ts": "tslint -c tslint.json \"src/**/*.ts\"",
+    "qa": "npm-run-all _typecheck _build",
+    "reset": "npx rimraf coverage dist embarkjs-*.tgz package",
+    "solo": "embark-solo"
+  },
+  "dependencies": {
+    "@babel/runtime-corejs3": "7.8.4",
+    "core-js": "3.6.4",
+    "embark-core": "^5.1.1-nightly.2",
+    "embarkjs": "^5.1.1-nightly.2",
+    "fs-extra": "8.1.0",
+    "snarkjs": "0.1.20"
+  },
+  "devDependencies": {
+    "embark-solo": "^5.1.1-nightly.2",
+    "eslint": "6.2.2",
+    "eslint-config-prettier": "6.1.0",
+    "eslint-plugin-prettier": "3.1.0",
+    "lodash.clonedeep": "4.5.0",
+    "npm-run-all": "4.1.5",
+    "rimraf": "3.0.0",
+    "tslint": "5.20.1",
+    "typescript": "3.7.2"
+  },
+  "engines": {
+    "node": ">=10.17.0",
+    "npm": ">=6.11.3",
+    "yarn": ">=1.19.1"
+  }
+}

packages/embarkjs/snark/src/browser/embarkjs-snark.ts

@@ -0,0 +1,43 @@
+/* global EmbarkJS */
+import { CircuitSetup, PluginConfig } from "..";
+import Circuit from "../circuit";
+
+export default class EmbarkJsSnark {
+  [key: string]: any;
+  private buildDir: string;
+  private buildDirUrl: string;
+  private contractsJsonDirUrl: string;
+  constructor(private setups: CircuitSetup[], private config: PluginConfig) {
+    this.buildDir = this.config.buildDir || "public/snarks/";
+    this.buildDirUrl = this.config.buildDirUrl || "/snarks/";
+    this.contractsJsonDirUrl = this.config.contractsJsonDirUrl || "/snarks/contracts/";
+  }
+
+  buildUrl(filepath: string) {
+    return filepath.replace(this.buildDir || "public/", this.buildDirUrl || "/");
+  }
+
+  public async init() {
+    for (const setup of this.setups) {
+      if (setup.config.exclude) {
+        continue;
+      }
+      if (!setup.provingKey) {
+        throw new Error("Error getting proving key: path not provided.");
+      }
+      if (!setup.verificationKey) {
+        throw new Error("Error getting verification key: path not provided.");
+      }
+      if (!setup.compiledCircuit) {
+        throw new Error("Error getting compiled circuit: path not provided.");
+      }
+      setup.compiledCircuit = await (await fetch(this.buildUrl(setup.compiledCircuit))).json();
+      setup.provingKey = await (await fetch(this.buildUrl(setup.provingKey))).json();
+      setup.verificationKey = await (await fetch(this.buildUrl(setup.verificationKey))).json();
+      const verifierContractJson = await (await fetch(`${this.contractsJsonDirUrl}${setup.verifierContractName}.json`)).json();
+      setup.verificationContract = new EmbarkJS.Blockchain.Contract(verifierContractJson);
+      const nameTitleCase = setup.name.charAt(0).toUpperCase() + setup.name.substr(1).toLowerCase();
+      this[nameTitleCase] = new Circuit(setup);
+    }
+  }
+}

packages/embarkjs/snark/src/circuit.ts

@@ -0,0 +1,109 @@
+import { CircuitSetup } from ".";
+import * as snarkjs from "snarkjs";
+const { unstringifyBigInts } = require("snarkjs/src/stringifybigint");
+
+const LOG_PREFIX = "[embarkjs-snark]: ";
+
+export default class Circuit {
+  constructor(private setup: CircuitSetup) {
+    this.setup.provingKey = unstringifyBigInts(this.setup.provingKey);
+    this.setup.verificationKey = unstringifyBigInts(this.setup.verificationKey);
+  }
+
+  /**
+   * Given public signals and a proof to prove those public signals can be verified,
+   * generates an array of inputs the can be used to call the verifyProof function
+   * in the verification contract (Solidity).
+   *
+   * @remarks Derived from the {@link https://github.com/iden3/snarkjs/blob/f2e5bc56b33aedbbbf7fed38b3f234d3d2b1adb7/cli.js#L365-L392 | "generatecall" snarkjs cli function}
+   *
+   * @param publicSignals - public inputs to be verified using the proof
+   * @param proof - the proof used to verify the inputs are valid
+   * @returns an array of solidity inputs that can be used to call the "verifyProof"
+   * function of the deployed vertificadtion contract
+   */
+  private generateSolidityInputs(publicSignals, proof): string[] {
+    publicSignals = unstringifyBigInts(publicSignals);
+    proof = unstringifyBigInts(proof);
+
+    const p256 = (n) => {
+      let nstr = n.toString(16);
+      while (nstr.length < 64) { nstr = "0" + nstr; }
+      nstr = `0x${nstr}`;
+      return nstr;
+    };
+
+    let inputs = "";
+    for (const publicSignal of publicSignals) {
+      if (inputs !== "") { inputs = inputs + ","; }
+      inputs = inputs + p256(publicSignal);
+    }
+
+    let S;
+    if ((typeof proof.protocol === "undefined") || (proof.protocol === "original")) {
+      S = [
+        [proof.pi_a[0], proof.pi_a[1]],
+        [proof.pi_ap[0], proof.pi_ap[1]],
+        [[proof.pi_b[0][1], proof.pi_b[0][0]], [proof.pi_b[1][1], proof.pi_b[1][0]]],
+        [proof.pi_bp[0], proof.pi_bp[1]],
+        [proof.pi_c[0], proof.pi_c[1]],
+        [proof.pi_cp[0], proof.pi_cp[1]],
+        [proof.pi_h[0], proof.pi_h[1]],
+        [proof.pi_kp[0], proof.pi_kp[1]]
+      ];
+    } else if ((proof.protocol === "groth") || (proof.protocol === "kimleeoh")) {
+      S = [
+        [proof.pi_a[0], proof.pi_a[1]],
+        [[proof.pi_b[0][1], proof.pi_b[0][0]], [proof.pi_b[1][1], proof.pi_b[1][0]]],
+        [proof.pi_c[0], proof.pi_c[1]]
+      ];
+    } else {
+      throw new Error("InvalidProof");
+    }
+
+    const two56ify = (arr: any[]): any[] => {
+      return arr.map(n => {
+        if (Array.isArray(n)) {
+          return two56ify(n);
+        }
+        return p256(n);
+      });
+    };
+    S = two56ify(S);
+    S.push([inputs]);
+    return S;
+  }
+
+  public async calculate(inputs: any) {
+    const circuit = new snarkjs.Circuit(this.setup.compiledCircuit);
+    const witness = circuit.calculateWitness(inputs);
+    const { proof, publicSignals } = snarkjs[this.setup.config.protocol].genProof(
+      this.setup.provingKey,
+      witness
+    );
+
+    return { proof, publicSignals };
+  }
+
+  public async verify(inputs: any) {
+    console.log(`${LOG_PREFIX}NOTE -- Private inputs will **not** be sent to the blockchain. They are used to calculate the witness and generate a proof.`);
+    if (!this.setup.verificationContract) {
+      return console.error(`Error verifying inputs, verification contract for '${this.setup.name}' not found.`);
+    }
+
+    console.log(`${LOG_PREFIX}Calculating witness and generating proof...`);
+    const { proof, publicSignals } = await this.calculate(inputs);
+    const solidityInputs = this.generateSolidityInputs(publicSignals, proof);
+
+    console.log(`${LOG_PREFIX}Verifying inputs on chain...`);
+    return await this.setup.verificationContract.methods.verifyProof(...solidityInputs).call();
+  }
+
+  public async verifyOffChain(inputs) {
+    console.log(`${LOG_PREFIX}Calculating witness and generating proof...`);
+    const { proof, publicSignals } = await this.calculate(inputs);
+
+    console.log(`${LOG_PREFIX}Verifying inputs off chain...`);
+    return snarkjs[this.setup.config.protocol].isValid(this.setup.verificationKey, proof, publicSignals);
+  }
+}

packages/embarkjs/snark/src/embarkjs-snark.ts

@@ -0,0 +1,31 @@
+import Circuit from "./circuit";
+import * as fs from "fs-extra";
+import { CircuitSetup } from ".";
+
+export default class EmbarkJsSnark {
+  [key: string]: any;
+  constructor(private setups: CircuitSetup[]) { }
+
+  public async init() {
+
+    for (const setup of this.setups) {
+      if (setup.config.exclude) {
+        continue;
+      }
+      if (!setup.provingKey) {
+        throw new Error("Error getting proving key: path not provided.");
+      }
+      if (!setup.verificationKey) {
+        throw new Error("Error getting verification key: path not provided.");
+      }
+      if (!setup.compiledCircuit) {
+        throw new Error("Error getting compiled circuit: path not provided.");
+      }
+      setup.compiledCircuit = await fs.readJson(setup.compiledCircuit);
+      setup.provingKey = await fs.readJson(setup.provingKey);
+      setup.verificationKey = await fs.readJson(setup.verificationKey);
+      const nameTitleCase = setup.name.charAt(0).toUpperCase() + setup.name.substr(1).toLowerCase();
+      this[nameTitleCase] = new Circuit(setup);
+    }
+  }
+}