js-waku/examples/eth-pm/src/crypto.ts

import '@ethersproject/shims';

import { PublicKeyMessage } from './messaging/wire';
import { hexToBuf, equalByteArrays, bufToHex } from 'js-waku/lib/utils';
import { generatePrivateKey, getPublicKey } from 'js-waku';
import * as sigUtil from 'eth-sig-util';

export interface KeyPair {
  privateKey: Uint8Array;
  publicKey: Uint8Array;
}

/**
 * Generate new encryption keypair.
 */
export async function generateEncryptionKeyPair(): Promise<KeyPair> {
  const privateKey = generatePrivateKey();
  const publicKey = getPublicKey(privateKey);
  return { privateKey, publicKey };
}

/**
 * Sign the encryption public key with Web3. This can then be published to let other
 * users know to use this encryption public key to encrypt messages for the
 * Ethereum Address holder.
 */
export async function createPublicKeyMessage(
  address: string,
  encryptionPublicKey: Uint8Array,
  providerRequest: (request: {
    method: string;
    params?: Array<any>;
  }) => Promise<any>
): Promise<PublicKeyMessage> {
  const signature = await signEncryptionKey(
    encryptionPublicKey,
    address,
    providerRequest
  );

  console.log('Asking wallet to sign Public Key Message');
  console.log('Public Key Message signed');

  return new PublicKeyMessage({
    encryptionPublicKey: encryptionPublicKey,
    ethAddress: hexToBuf(address),
    signature: hexToBuf(signature),
  });
}

function buildMsgParams(encryptionPublicKey: Uint8Array, fromAddress: string) {
  return JSON.stringify({
    domain: {
      chainId: 1,
      name: 'Ethereum Private Message over Waku',
      version: '1',
    },
    message: {
      encryptionPublicKey: bufToHex(encryptionPublicKey),
      ownerAddress: fromAddress,
    },
    // Refers to the keys of the *types* object below.
    primaryType: 'PublishEncryptionPublicKey',
    types: {
      EIP712Domain: [
        { name: 'name', type: 'string' },
        { name: 'version', type: 'string' },
        { name: 'chainId', type: 'uint256' },
      ],
      PublishEncryptionPublicKey: [
        { name: 'encryptionPublicKey', type: 'string' },
        { name: 'ownerAddress', type: 'string' },
      ],
    },
  });
}

export async function signEncryptionKey(
  encryptionPublicKey: Uint8Array,
  fromAddress: string,
  providerRequest: (request: {
    method: string;
    params?: Array<any>;
    from?: string;
  }) => Promise<any>
): Promise<Uint8Array> {
  const msgParams = buildMsgParams(encryptionPublicKey, fromAddress);

  const result = await providerRequest({
    method: 'eth_signTypedData_v3',
    params: [fromAddress, msgParams],
    from: fromAddress,
  });

  console.log('TYPED SIGNED:' + JSON.stringify(result));

  return hexToBuf(result);
}

/**
 * Validate that the Encryption Public Key was signed by the holder of the given Ethereum address.
 */
export function validatePublicKeyMessage(msg: PublicKeyMessage): boolean {
  const recovered = sigUtil.recoverTypedSignature_v4({
    data: JSON.parse(
      buildMsgParams(msg.encryptionPublicKey, '0x' + bufToHex(msg.ethAddress))
    ),
    sig: '0x' + bufToHex(msg.signature),
  });

  console.log('Recovered', recovered);
  console.log('ethAddress', '0x' + bufToHex(msg.ethAddress));

  return equalByteArrays(recovered, msg.ethAddress);
}