Aes constructor
Implementation
Aes(this.derivedKey, Uint8List hmacDerivedKey, this.aesKeyStrength,
{this.encrypt = false}) {
aesEngine = AESEngine();
aesEngine!.init(true, KeyParameter(derivedKey));
_macGen = AesCipherUtil.getMacBasedPRF(hmacDerivedKey);
}