RSA Key generation in iPhone 5s does not work

[Vanethos]

I tried to create RSA keypair using @proteye 's gist: https://gist.github.com/proteye/982d9991922276ccfb011dfc55443d74, even creating a isolate for it, but on the iPhone 5s and iPad air it can't get past the keyGenerator.generateKeyPair(); line.

Code:

AsymmetricKeyPair<PublicKey, PrivateKey> computeRSAKeyPair(
    SecureRandom secureRandom) {

  var rsapars = new RSAKeyGeneratorParameters(BigInt(65537), 2048, 12);
  var params = new ParametersWithRandom(rsapars, secureRandom);

  var keyGenerator = new RSAKeyGenerator();
  keyGenerator.init(params);
  /// CODE BLOCKS IN THE FOLLOWING LINE:
  return keyGenerator.generateKeyPair();
}

  Future<AsymmetricKeyPair<PublicKey, PrivateKey>> getRSAKeyPair(
      SecureRandom secureRandom) async {
    return await compute(computeRSAKeyPair, secureRandom);
  }

SecureRandom getSecureRandom() {
    var secureRandom = FortunaRandom();
    var random = Random.secure();
    List<int> seeds = [];
    for (int i = 0; i < 32; i++) {
      seeds.add(random.nextInt(255));
    }
    secureRandom.seed(new KeyParameter(new Uint8List.fromList(seeds)));
    return secureRandom;
  }

This works on OnePlus 6,and the android and ios simulator on the mac.

Am I doing something wrong? Is this not the correct way for generating a key-pair?