Merge pull request #935 from privacy-scaling-explorations/refactor/cr…

…ypto-cleanup

refactor(crypto): improve package structure

crypto/ts/AccQueue.ts

@@ -2,9 +2,10 @@ import { OptimisedMT as IncrementalQuinTree } from "optimisedmt";
 
 import assert from "assert";
 
+import type { Leaf, Queue, StringifiedBigInts } from "./types";
+
 import { deepCopyBigIntArray, stringifyBigInts, unstringifyBigInts } from "./bigIntUtils";
-import { sha256Hash, hashLeftRight, hash5 } from "./crypto";
-import { Leaf, Queue, StringifiedBigInts } from "./types";
+import { sha256Hash, hashLeftRight, hash5 } from "./hashing";
 import { calcDepthFromNumLeaves } from "./utils";
 
 /**

crypto/ts/__tests__/Crypto.test.ts

@@ -1,10 +1,8 @@
 import { expect } from "chai";
 
+import { G1Point, G2Point, genRandomBabyJubValue } from "../babyjub";
 import { SNARK_FIELD_SIZE } from "../constants";
 import {
-  genPubKey,
-  genKeypair,
-  genEcdhSharedKey,
   sha256Hash,
   hash2,
   hash3,
@@ -13,19 +11,13 @@ import {
   hash13,
   hashLeftRight,
   hashN,
+  hashOne,
   poseidonT3,
   poseidonT4,
   poseidonT5,
   poseidonT6,
-  genRandomSalt,
-  G1Point,
-  G2Point,
-  hashOne,
-  genRandomBabyJubValue,
-  genPrivKey,
-  packPubKey,
-  unpackPubKey,
-} from "../crypto";
+} from "../hashing";
+import { genPubKey, genKeypair, genEcdhSharedKey, genRandomSalt, genPrivKey, packPubKey, unpackPubKey } from "../keys";
 
 describe("Crypto", function test() {
   this.timeout(100000);

crypto/ts/babyjub.ts

@@ -0,0 +1,131 @@
+import assert from "assert";
+import { randomBytes } from "crypto";
+
+import { SNARK_FIELD_SIZE } from "./constants";
+import { PrivKey } from "./types";
+
+/**
+ * @notice A class representing a point on the first group (G1)
+ * of the Jubjub curve
+ */
+export class G1Point {
+  x: bigint;
+
+  y: bigint;
+
+  /**
+   * Create a new instance of G1Point
+   * @param x the x coordinate
+   * @param y the y coordinate
+   */
+  constructor(x: bigint, y: bigint) {
+    assert(x < SNARK_FIELD_SIZE && x >= 0, "G1Point x out of range");
+    assert(y < SNARK_FIELD_SIZE && y >= 0, "G1Point y out of range");
+    this.x = x;
+    this.y = y;
+  }
+
+  /**
+   * Check whether two points are equal
+   * @param pt the point to compare with
+   * @returns whether they are equal or not
+   */
+  equals(pt: G1Point): boolean {
+    return this.x === pt.x && this.y === pt.y;
+  }
+
+  /**
+   * Return the point as a contract param in the form of an object
+   * @returns the point as a contract param
+   */
+  asContractParam(): { x: string; y: string } {
+    return {
+      x: this.x.toString(),
+      y: this.y.toString(),
+    };
+  }
+}
+
+/**
+ * @notice A class representing a point on the second group (G2)
+ * of the Jubjub curve. This is usually an extension field of the
+ * base field of the curve.
+ */
+export class G2Point {
+  x: bigint[];
+
+  y: bigint[];
+
+  /**
+   * Create a new instance of G2Point
+   * @param x the x coordinate
+   * @param y the y coordinate
+   */
+  constructor(x: bigint[], y: bigint[]) {
+    this.checkPointsRange(x, "x");
+    this.checkPointsRange(y, "y");
+
+    this.x = x;
+    this.y = y;
+  }
+
+  /**
+   * Check whether two points are equal
+   * @param pt the point to compare with
+   * @returns whether they are equal or not
+   */
+  equals(pt: G2Point): boolean {
+    return this.x[0] === pt.x[0] && this.x[1] === pt.x[1] && this.y[0] === pt.y[0] && this.y[1] === pt.y[1];
+  }
+
+  /**
+   * Return the point as a contract param in the form of an object
+   * @returns the point as a contract param
+   */
+  asContractParam(): { x: string[]; y: string[] } {
+    return {
+      x: this.x.map((n) => n.toString()),
+      y: this.y.map((n) => n.toString()),
+    };
+  }
+
+  /**
+   * Check whether the points are in range
+   * @param x the x coordinate
+   * @param type the type of the coordinate
+   */
+  private checkPointsRange(x: bigint[], type: "x" | "y") {
+    assert(
+      x.every((n) => n < SNARK_FIELD_SIZE && n >= 0),
+      `G2Point ${type} out of range`,
+    );
+  }
+}
+
+/**
+ * Returns a BabyJub-compatible random value. We create it by first generating
+ * a random value (initially 256 bits large) modulo the snark field size as
+ * described in EIP197. This results in a key size of roughly 253 bits and no
+ * more than 254 bits. To prevent modulo bias, we then use this efficient
+ * algorithm:
+ * http://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/lib/libc/crypt/arc4random_uniform.c
+ * @returns A BabyJub-compatible random value.
+ */
+export const genRandomBabyJubValue = (): bigint => {
+  // Prevent modulo bias
+  // const lim = BigInt('0x10000000000000000000000000000000000000000000000000000000000000000')
+  // const min = (lim - SNARK_FIELD_SIZE) % SNARK_FIELD_SIZE
+  const min = BigInt("6350874878119819312338956282401532410528162663560392320966563075034087161851");
+
+  let privKey: PrivKey = SNARK_FIELD_SIZE;
+
+  do {
+    const rand = BigInt(`0x${randomBytes(32).toString("hex")}`);
+
+    if (rand >= min) {
+      privKey = rand % SNARK_FIELD_SIZE;
+    }
+  } while (privKey >= SNARK_FIELD_SIZE);
+
+  return privKey;
+};