@exodus/transform-storage

const storage = transformStorage({
  storage: storage.namespace('highly-secret'),
  onRead: async (ciphertext) => {
    const buffer = await decryptSecretBox({ data: Buffer.from(ciphertext, 'base64') });
    return JSON.parse(buffer.toString());
  },
  onWrite: async (value) => {
    const buffer = await encryptSecretBox({ data: JSON.stringify(value) });
    return buffer.toString('base64');
  },
});