Decrypt Upcoming Text Flutter

Question

I just want to enter string and on press decrypt it. this is my app, but I can't decrypt the string cause _cipher.text type 'String'. it's type should be 'Encrypted'

onPressed: ()  {
                setState(() {
                  final k = Key.fromUtf8('1234567891011123');
                  final iv = IV.fromLength(16);
                  final encrypter = Encrypter(AES(k));
                  final decrypted = encrypter.decrypt(_cipher.text, iv: iv);
                  _plain.text = decrypted;
                });
              },

I don't want to use final crypted = encrypter.encrypt(_cipher.text, iv: iv); cause it comes encrypted.

Answer 1

You can't just directly decrypt the string. You need to pass in the encrypted one into decrypt otherwise it would give block size error in most of the cases.

import 'package:encrypt/encrypt.dart';

void main() {
  final cipher = 'Lorem ipsum dolor sit amet';
  final k = Key.fromUtf8('1234567891011123');
  final iv = IV.fromLength(16);

  final encrypter = Encrypter(AES(k));

  final encrypted = encrypter.encrypt(cipher, iv: iv);
  final decrypted = encrypter.decrypt(encrypted, iv: iv);

  print(encrypted.base64);
  print(decrypted);
}

If you have manually set the cipher as base16 or base64 string, you can do this :

import 'package:encrypt/encrypt.dart';

void main() {
  final cipher = 'Xg4+gtUDU0Hd9uMUWU7IJtjxvocKzIOJwumyzbY5n40=';
  final k = Key.fromUtf8('1234567891011123');
  final iv = IV.fromLength(16);

  final encrypter = Encrypter(AES(k));

  final decrypted = encrypter.decrypt(Encrypted.fromBase64(cipher), iv: iv);

  print(decrypted);
}

Edit: If you are taking the cipher input from user, you need to validate that using the encrypter if it's a base16 or base64 only then you can continue to decrypt using Encrypted.fromBase64(cipher) or Encrypted.fromBase16(cipher)