Use isZeroUint8Array to check for empty bytes

src/blst/privateKey.ts

@@ -1,9 +1,10 @@
 import * as blst from "@chainsafe/blst";
-import {bytesToHex, hexToBytes, randomBytes} from "../helpers";
+import {bytesToHex, hexToBytes, isZeroUint8Array, randomBytes} from "../helpers";
 import {SECRET_KEY_LENGTH} from "../constants";
 import {IPrivateKey} from "../interface";
 import {PublicKey} from "./publicKey";
 import {Signature} from "./signature";
+import {ZeroPrivateKeyError} from "../errors";
 
 export class PrivateKey implements IPrivateKey {
   readonly value: blst.SecretKey;
@@ -13,6 +14,11 @@ export class PrivateKey implements IPrivateKey {
   }
 
   static fromBytes(bytes: Uint8Array): PrivateKey {
+    // draft-irtf-cfrg-bls-signature-04 does not allow SK == 0
+    if (isZeroUint8Array(bytes)) {
+      throw new ZeroPrivateKeyError();
+    }
+
     const sk = blst.SecretKey.fromBytes(bytes);
     return new PrivateKey(sk);
   }

src/constants.ts

@@ -3,5 +3,3 @@ export const SIGNATURE_LENGTH = 96;
 export const FP_POINT_LENGTH = 48;
 export const PUBLIC_KEY_LENGTH = FP_POINT_LENGTH;
 export const G2_HASH_PADDING = 16;
-export const EMPTY_PUBLIC_KEY = new Uint8Array(PUBLIC_KEY_LENGTH);
-export const EMPTY_SIGNATURE = new Uint8Array(SIGNATURE_LENGTH);

src/helpers/utils.ts

@@ -3,14 +3,6 @@ import randomBytes from "randombytes";
 // Single import to ease changing this lib if necessary
 export {randomBytes};
 
-export function isEqualBytes(a: Buffer | Uint8Array, b: Buffer | Uint8Array): boolean {
-  return toBuffer(a).equals(toBuffer(b));
-}
-
-export function toBuffer(input: Uint8Array): Buffer {
-  return Buffer.from(input.buffer, input.byteOffset, input.length);
-}
-
 /**
  * Validate bytes to prevent confusing WASM errors downstream if bytes is null
  */
@@ -24,3 +16,7 @@ export function validateBytes(
     }
   }
 }
+
+export function isZeroUint8Array(bytes: Uint8Array): boolean {
+  return bytes.every((byte) => byte === 0);
+}

src/herumi/publicKey.ts

@@ -1,7 +1,7 @@
 import {PublicKeyType} from "bls-eth-wasm";
 import {getContext} from "./context";
-import {EMPTY_PUBLIC_KEY, PUBLIC_KEY_LENGTH} from "../constants";
-import {bytesToHex, hexToBytes, isEqualBytes} from "../helpers";
+import {PUBLIC_KEY_LENGTH} from "../constants";
+import {bytesToHex, hexToBytes, isZeroUint8Array} from "../helpers";
 import {IPublicKey} from "../interface";
 import {ZeroPublicKeyError} from "../errors";
 
@@ -23,7 +23,7 @@ export class PublicKey implements IPublicKey {
 
     const context = getContext();
     const publicKey = new context.PublicKey();
-    if (!isEqualBytes(EMPTY_PUBLIC_KEY, bytes)) {
+    if (!isZeroUint8Array(bytes)) {
       publicKey.deserialize(bytes);
     }
     return new PublicKey(publicKey);

src/herumi/signature.ts

@@ -1,8 +1,8 @@
-import {SIGNATURE_LENGTH, EMPTY_SIGNATURE} from "../constants";
+import {SIGNATURE_LENGTH} from "../constants";
 import {SignatureType} from "bls-eth-wasm";
 import {getContext} from "./context";
 import {PublicKey} from "./publicKey";
-import {bytesToHex, hexToBytes, isEqualBytes} from "../helpers";
+import {bytesToHex, hexToBytes, isZeroUint8Array} from "../helpers";
 import {ISignature} from "../interface";
 
 export class Signature implements ISignature {
@@ -23,7 +23,7 @@ export class Signature implements ISignature {
 
     const context = getContext();
     const signature = new context.Signature();
-    if (!isEqualBytes(EMPTY_SIGNATURE, bytes)) {
+    if (!isZeroUint8Array(bytes)) {
       signature.deserialize(bytes);
     }
     return new Signature(signature);

test/unit/helpers/bytes.test.ts

@@ -0,0 +1,29 @@
+import {expect} from "chai";
+import {isZeroUint8Array} from "../../../src/helpers/utils";
+
+describe("helpers / bytes", () => {
+  describe("isZeroUint8Array", () => {
+    const testCases: {isZero: boolean; hex: string}[] = [
+      {hex: "0x00", isZero: true},
+      {hex: "0x" + "00".repeat(32), isZero: true},
+      {hex: "0x" + "00".repeat(96), isZero: true},
+      {hex: "0x" + "00".repeat(31) + "01", isZero: false},
+      {
+        hex: "0xb6f21199594b56d77670564bf422cb331d5281ca2c1f9a45588a56881d8287ef8619efa6456d6cd2ef61306aa5b21311",
+        isZero: false,
+      },
+    ];
+
+    for (const {hex, isZero} of testCases) {
+      it(`${hex} isZero = ${isZero}`, () => {
+        const bytes = hexToBytesNode(hex);
+        console.log(bytes);
+        expect(isZeroUint8Array(bytes)).to.equal(isZero);
+      });
+    }
+  });
+});
+
+function hexToBytesNode(hex: string): Buffer {
+  return Buffer.from(hex.replace("0x", ""), "hex");
+}