src/crypt/fast-aes-key.ts

export default class FastAESKey {
  private subtle: any;
  private key: ArrayBuffer;

  constructor (subtle, key) {
    this.subtle = subtle;
    this.key = key;
  }

  expandKey () {
    return this.subtle.importKey('raw', this.key, { name: 'AES-CBC' }, false, ['encrypt', 'decrypt']);
  }
}