Add crypto util

lib/utils/crypto_util.dart

@@ -0,0 +1,23 @@
+import 'dart:convert';
+import 'dart:math';
+
+import 'package:encrypt/encrypt.dart';
+
+class CryptoUtil {
+  static final Random _random = Random.secure();
+
+  static String createCryptoRandomString([int length = 32]) {
+    var values = List<int>.generate(length, (i) => _random.nextInt(256));
+    return base64Url.encode(values);
+  }
+
+  static String encrypt(String plainText, String key) {
+    final encrypter = Encrypter(AES(Key.fromUtf8(key)));
+    return encrypter.encrypt(plainText).base64;
+  }
+
+  static String decrypt(String cipherText, String key) {
+    final encrypter = Encrypter(AES(Key.fromUtf8(key)));
+    return encrypter.decrypt(Encrypted.fromBase64(cipherText));
+  }
+}

pubspec.lock

@@ -22,6 +22,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.6.0"
+  asn1lib:
+    dependency: transitive
+    description:
+      name: asn1lib
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "0.6.5"
   async:
     dependency: transitive
     description:
@@ -148,6 +155,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "0.0.4"
+  encrypt:
+    dependency: "direct main"
+    description:
+      name: encrypt
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "4.0.2"
   esys_flutter_share:
     dependency: "direct main"
     description:
@@ -443,6 +457,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.0.2"
+  pointycastle:
+    dependency: transitive
+    description:
+      name: pointycastle
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.2"
   process:
     dependency: transitive
     description:

pubspec.yaml

@@ -22,6 +22,7 @@ dependencies:
 
   # The following adds the Cupertino Icons font to your application.
   # Use with the CupertinoIcons class for iOS style icons.
+  encrypt: ^4.0.2
   cupertino_icons: ^0.1.2
   photo_manager: ^0.5.7
   provider: ^3.1.0