Asymmetric cryptography without revealing the private key

I am trying to get the public key of a connected wallet, use it to encrypt data, and then use the private key of the same user to decrypt it. So far, I have used the following to get the public key (all code is in react.js):

let encryptionPublicKey;
window.ethereum .request({ method: 'eth_getEncryptionPublicKey', params: [accounts[0]], // you must have access to the specified account })
.then((result) => { encryptionPublicKey = result; console.log(encryptionPublicKey); this.setState({encryptionPublicKey}) })
.catch((error) => { if (error.code === 4001) { // EIP-1193 userRejectedRequest error console.log("We can't encrypt anything without the key."); } else { console.error(error); } });

Then, I use this function to encrypt:

async encrypt(content){
/* Encrypting */
const encryptedMessage = ethUtil.bufferToHex(
{ data: 'Hello world!' },
return encryptedMessage;

I am using 'Hello World' just to test for starters.

I get this error "Cannot read properties of undefined (reading 'bufferToHex')". Sometimes when I change a few things, I get this "Cannot read properties of undefined (reading 'encrypt')". FYI, I plan to use this function to decrypt the encrypted data.

/* Decrypting */
let decryptedResult = "";
method: 'eth_decrypt',
params: [encryptedContent, this.state.account],
.then((decryptedMessage) =>
// console.log('The decrypted message is:', decryptedMessage);
decryptedResult = decryptedMessage
.catch((error) => console.log(error.message));

Here are the relevant dependencies:
import {ethUtil, sigUtil} from 'ethereumjs-util';
import {encrypt} from 'eth-sig-util';

I would appreciate some assistance.
Thank you.