Add PoC for rsa key generation and encrypt/decryption using it

We want to stop relying on openssl in order to generate the keys. Using a
c library for this complicates the entire build process, and makes
everything so so much more complicated.

lib/main2.dart

@@ -0,0 +1,48 @@
+import 'dart:math';
+import 'dart:typed_data';
+
+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';
+import 'package:steel_crypt/steel_crypt.dart';
+
+void main() {
+  var encrypter = RsaCrypt();
+  var keyPair = _getRsaKeyPair(_getSecureRandom());
+  var publicKey = keyPair.publicKey as RSAPublicKey;
+  var privateKey = keyPair.privateKey as RSAPrivateKey;
+
+  var crypted4 = encrypter.encrypt('word', keyPair.publicKey);
+  print("Encryped: $crypted4");
+  print("Decrypted: " + encrypter.decrypt(crypted4, keyPair.privateKey));
+
+  var ps = encrypter.encodeKeyToString(publicKey);
+  print("PS: $ps");
+
+  var priv = encrypter.encodeKeyToString(privateKey);
+  print("Priv: $priv");
+}
+
+SecureRandom _getSecureRandom() {
+  final secureRandom = FortunaRandom();
+  final random = Random.secure();
+  var seeds = List<int>.of([]);
+  for (var i = 0; i < 32; i++) {
+    seeds.add(random.nextInt(255));
+  }
+  secureRandom.seed(KeyParameter(Uint8List.fromList(seeds)));
+  return secureRandom;
+}
+
+///Create RSA keypair given SecureRandom.
+AsymmetricKeyPair<PublicKey, PrivateKey> _getRsaKeyPair(
+  SecureRandom secureRandom,
+) {
+  // See URL for why these values
+  // https://crypto.stackexchange.com/questions/15449/rsa-key-generation-parameters-public-exponent-certainty-string-to-key-count/15450#15450?newreg=e734eafab61e42f1b155b62839ccce8f
+  final rsapars = RSAKeyGeneratorParameters(BigInt.from(65537), 2048 * 2, 5);
+  final params = ParametersWithRandom(rsapars, secureRandom);
+  final keyGenerator = RSAKeyGenerator();
+  keyGenerator.init(params);
+  return keyGenerator.generateKeyPair();
+}