Unhandled Exception: Invalid argument: Instance of 'Encrypted'

I am trying to add encryption to my chat application . but facing an issue while doing so , i cant add the data to firebase , it shows an error Unhandled Exception: Invalid argument: Instance of 'Encrypted'. how can i send a message that is encrypted from client side and send it to firebase and then receive the message , then decrypt it . because i am using the library encrypt 5.0.0 for this and to decrypt it , it only accept the Encrypted as parameter .

here is class for encryption and decryption .

import 'package:encrypt/encrypt.dart' as encrypt;
class MyEncryptionDecryption{

  ///for encrption

 static final key = encrypt.Key.fromLength(32);
 static final iv = encrypt.IV.fromLength(16);
 static final  encrypter = encrypt.Encrypter(encrypt.AES(key));


  static encryptAES(message ){

   final encrypted =  encrypter.encrypt(message ,iv: iv);
      print(encrypted.base16);
      print(encrypted.base64);
      return encrypted;
  }
  static decryptedAES(message){

    return   encrypter.decrypt(message,iv: iv);

  }
  
}

using it to send message to firebase as this ..

var aes = MyEncryptionDecryption.encryptAES(message);
      Map<String, dynamic> messageInfoMap = {
        "message": aes,
        "sendBy": myUserName,
        "ts": lastMessageTs,
        "imgUrl": myProfilePic
      };


      DatabaseMethods()
          .addMessage(chatRoomId, messageId, messageInfoMap)
          .then((value) {


        Map<String, dynamic> lastMessageInfoMap = {
          "lastMessage": aes,
          "lastMessageSendTs": lastMessageTs,
          "lastMessageSendBy": myUserName,
          "readStatus" : false ,
          "count" : count,
          "show" : true,
        };

        DatabaseMethods().updateLastMessageSend(chatRoomId, lastMessageInfoMap);

and here are the Database functions ..

Future addMessage(String chatRoomId , String messageId,messageInfoMap) async {
   return await FirebaseFirestore.instance.
   collection("chatrooms").
   doc(chatRoomId).collection('chats').doc(messageId).set(messageInfoMap);
 }
 updateLastMessageSend(String chatRoomId, lastMessageInfoMap){
   return FirebaseFirestore
       .instance.collection('chatrooms').doc(chatRoomId)
       .update(lastMessageInfoMap);
 }