i am using encrypt package to encrypt and decrypt my plaintext. i have followed the examples in https://pub.dev/packages/encrypt. it encrypts and decrypts successfully until i hot restart my app. after i hot restart, the it returns the following error: Invalid or corrupted pad block. the plaintext are encrypted and uploaded to Firestore and for decryption, it is retrieved from Firestore and decrypted. tia for all inputs

import 'package:encrypt/encrypt.dart';

// Generate a key and IV for encryption
final Key key = Key.fromUtf8('my 32 length key................');
final IV iv = IV.fromLength(16);

final Encrypter encrypter = Encrypter(AES(key));

// Encrypt message
String encryptMessage(String plainTextMessage) {
  final Encrypted encrypted = encrypter.encrypt(plainTextMessage, iv: iv);
  return encrypted.base64;
}

// Decrypt message
String decryptMessage(String encryptedMessage) {
  final Encrypted encrypted = Encrypted.fromBase64(encryptedMessage);
  final String decrypted = encrypter.decrypt(encrypted, iv: iv);
  return decrypted;
}