Encriptar y desencriptar crypto API

index.js

function getMessageEncoding(message) {
  let enc = new TextEncoder();
  return enc.encode(message);
}
function bufferToStr(buff) {
  return String.fromCharCode.apply(null, new Uint8Array(buff));
}
async function main() {
  const counter = window.crypto.getRandomValues(new Uint8Array(16));

  const key = Buffer.from("holasoydavid1234");

  const key_encoded = await crypto.subtle.importKey(
    "raw",
    key.buffer,
    "AES-CTR",
    false,
    ["encrypt", "decrypt"]
  );
  const msg = "mi mensaje secreto";
  const encrypted = await window.crypto.subtle.encrypt(
    {
      name: "AES-CTR",
      counter: counter,
      length: 64
    },
    key_encoded,
    getMessageEncoding(msg)
  );
  console.log(encrypted, "1");
  const decrypted = await window.crypto.subtle.decrypt(
    {
      name: "AES-CTR",
      counter: counter,
      length: 64
    },
    key_encoded,
    encrypted
  );
  console.log(bufferToStr(decrypted));
}
main();