WebCrypto encrypt/decrypt

webcrypto.js

const ENCRYPT_PASSWORD = 'SEbSk7s9AxpUDiPgljlmYpRvr3yNVurYqmBm82swjhU';

let encryptionKey;
async function getEncryptionKey() {
  if (encryptionKey) {
    return encryptionKey;
  }

  const exported = {
    alg: 'A256GCM',
    ext: true,
    k: ENCRYPT_PASSWORD,
    key_ops: ['encrypt', 'decrypt'],
    kty: 'oct',
  };

  encryptionKey = await crypto.subtle.importKey(
    'jwk',
    exported,
    { name: 'AES-GCM' },
    exported.ext,
    exported.key_ops
  );

  return encryptionKey;
}

async function encrypt(string) {
  const encoded = new TextEncoder().encode(string);
  const iv = crypto.getRandomValues(new Uint8Array(12));
  const ivString = iv.join('e');

  const encrypted = await crypto.subtle.encrypt(
    {
      name: 'AES-GCM',
      iv: iv,
    },
    await getEncryptionKey(),
    encoded
  );

  const encryptedString = new Uint8Array(encrypted).join('e');

  return `${encryptedString}.${ivString}`;
}

async function decrypt(string) {
  const [cipherText, iv] = string.split('.');

  const ivArray = new Uint8Array(iv.split('e').map(i => parseInt(i)));
  const cipherTextArray = new Uint8Array(
    cipherText.split('e').map(i => parseInt(i))
  );

  const buffer = await crypto.subtle.decrypt(
    {
      name: 'AES-GCM',
      iv: ivArray,
    },
    await getEncryptionKey(),
    cipherTextArray
  );

  return new TextDecoder().decoder(buffer);
}