How to decrypt of the encrypted value in dart? - encryption

Question

I am testing the Cryptographic hashing functions for Dart.  I can't find any information about DECRYPTION?
Can anyone show me how to decryption of the encrypted value?
And this is example;
import 'dart:convert';
import 'package:crypto/crypto.dart';
void main() async {
  var key = utf8.encode('p#ssw0rd');
  var bytes = utf8.encode("Dart and Aqueduct makes my life easier. Thank you.");
  // TODO: ENCRYPTION
  var hmacSha256 = new Hmac(sha256, key); // HMAC-SHA256
  var digest = hmacSha256.convert(bytes);
 
  print(“————ENCRYPTION—————“);
  print("HMAC digest as bytes: ${digest.bytes}");
  print("HMAC digest as hex string: $digest");
  print('\r\n');
  // TODO: DECRYPTION
     ????????????
  print(“————DECRYPTION—————“);
  print(?????????);
}

Answer 1

The easiest way IMO is to use encrypt:
import 'package:encrypt/encrypt.dart';
final key = Key.fromUtf8('put32charactershereeeeeeeeeeeee!'); //32 chars
final iv = IV.fromUtf8('put16characters!'); //16 chars
//encrypt
String encryptMyData(String text) {
final e = Encrypter(AES(key, mode: AESMode.cbc));
final encrypted_data = e.encrypt(text, iv: iv);
return encrypted_data.base64;
}
//dycrypt
String decryptMyData(String text) {
final e = Encrypter(AES(key, mode: AESMode.cbc));
final decrypted_data = e.decrypt(Encrypted.fromBase64(text), iv: iv);
return decrypted_data;
}

Answer 2

An HMAC is a message authentication code. It is a digest used to verify that a message has not been tampered with, similar to a signature. It is constructed using a one-way hash function, in this case SHA256. It is not an encryption, and it cannot be reversed, therefore the value you have cannot be decrypted.
The only thing you can do with an HMAC is, given the HMAC and the corresponding plain-text, verifying the origin of the plain-text and that it has not been tampered with.
Looking at the GitHub page for the Dart crypto library, it looks like it only supports digest algorithms. There are no encryption algorithms listed, so you will need to use a different library if you want to do two-way encryption which can actually be decrypted. The Cipher library looks like it could be promising in this regard.

Answer 3

PointyCastle (https://pub.dartlang.org/packages/pointycastle) has been recommended in the past, but it appears to have not yet been updated for Dart 2. :(

Answer 4

Well actually searching a lot couldn't find anything better than this. The encrypt 0.2.0 new and has Dart 2 support. https://pub.dartlang.org/packages/encrypt#-installing-tab-
I need to something that makes My Flutter Mobile App and Aqueduct can share secure communication. Leo Cavalcante is a great guy. While we were talking yesterday he comes up quick answer. So this is another love of Dart. Because every people support each other.
It Supports:
AES (Block Cipher)
Salsa20 (Stream Cipher)
RSA (Asymmetric) (working)
Use this package as a library
Depend on it
Add this to your package's pubspec.yaml file:
dependencies:
encrypt: "^0.2.0"
Install it
You can install packages from the command line:
with pub:
$ pub get
with Flutter:
$ flutter packages get
Alternatively, your editor might support pub get or flutter packages get. Check the docs for your editor to learn more.
Import it
Now in your Dart code, you can use:
import 'package:encrypt/encrypt.dart';

Answer 5

If anyone is looking for a rather simpler solution without having to depend on the library, I have written my custom solution on encrypting and decrypting string values in dart, which obliviously can be used in flutter too. The code is rather straightforward, so I am not going to talk about the code on how it works. The strategy used in encryption is x-or encryption-decryption.
var encryptionKey ='your encryption key';
static String encrypt(String data) {
var charCount = data.length;
var encrypted = [];
var kp = 0;
var kl = encryptionKey.length - 1;
for (var i = 0; i < charCount; i++) {
var other = data[i].codeUnits[0] ^ encryptionKey[kp].codeUnits[0];
encrypted.insert(i, other);
kp = (kp < kl) ? (++kp) : (0);
}
return dataToString(encrypted);
}
static String decrypt(data) {
return encrypt(data);
}
static String dataToString(data) {
var s = "";
for (var i = 0; i < data.length; i++) {
s += String.fromCharCode(data[i]);
}
return s;
}