RsaKey: Add a method to generate the key in another isolate

This way we won't be blocking the main thread.

lib/ssh/rsa_key_pair.dart

@@ -1,8 +1,11 @@
+import 'dart:async';
 import 'dart:convert';
 import 'dart:math';
 import 'dart:typed_data';
 
+import 'package:gitjournal/error_reporting.dart';
 import 'package:gitjournal/ssh/binary_length_value.dart';
+import 'package:gitjournal/utils/logger.dart';
 import 'package:steel_crypt/PointyCastleN/key_generators/rsa_key_generator.dart';
 import 'package:steel_crypt/PointyCastleN/pointycastle.dart';
 import 'package:steel_crypt/PointyCastleN/random/fortuna_random.dart';
@@ -10,6 +13,7 @@ import 'package:steel_crypt/steel_crypt.dart';
 import 'package:meta/meta.dart';
 
 import 'package:ssh_key/ssh_key.dart' as ssh_key;
+import 'package:isolate/isolate_runner.dart';
 
 class RsaKeyPair {
   RSAPublicKey publicKey;
@@ -83,6 +87,19 @@ class RsaKeyPair {
     var encrypter = RsaCrypt();
     return encrypter.encodeKeyToString(privateKey);
   }
+
+  static Future<RsaKeyPair> generateAsync() async {
+    IsolateRunner iso = await IsolateRunner.spawn();
+    try {
+      return await iso.run(_gen, null);
+    } catch (e) {
+      Log.e(e);
+      logException(e, StackTrace.current);
+      return null;
+    } finally {
+      iso.close();
+    }
+  }
 }
 
 SecureRandom _getSecureRandom() {
@@ -108,3 +125,7 @@ AsymmetricKeyPair<PublicKey, PrivateKey> _getRsaKeyPair(
   keyGenerator.init(params);
   return keyGenerator.generateKeyPair();
 }
+
+FutureOr<RsaKeyPair> _gen(void _) async {
+  return RsaKeyPair.generate();
+}

pubspec.lock

@@ -378,6 +378,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "0.3.3"
+  isolate:
+    dependency: "direct main"
+    description:
+      name: isolate
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.3"
   js:
     dependency: transitive
     description:

pubspec.yaml

@@ -48,6 +48,7 @@ dependencies:
   cached_network_image: ^2.1.0+1
   ssh_key:
     git: https://github.com/GitJournal/ssh_key.git
+  isolate: ^2.0.3
 
 dev_dependencies:
   flutter_launcher_icons: "^0.7.2"

test/rsa_key_pair_test.dart

@@ -8,6 +8,11 @@ void main() {
     expect(pair.isValid(), true);
   });
 
+  test('Should async generate and verify keys', () async {
+    var pair = await RsaKeyPair.generateAsync();
+    expect(pair.isValid(), true);
+  });
+
   var publicKeySingleLine =
       'ssh-rsa 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';
   var publicKeySsh2 = '''---- BEGIN SSH2 PUBLIC KEY ----