Decode PrivateKey

[1AlexFix1]

Hi, I have a problem, because I can not decrypt the information with a private key if it was encrypted somewhere else, swift or kotlin, the output is porridge. maybe i'm not getting my private key right?

 RSAPrivateKey pemToPrivKey(pemPrivKey) {
    try {
      ASN1Parser asn1Parser = ASN1Parser(_decodePEM(pemPrivKey));
      ASN1Sequence asn1sequence = asn1Parser.nextObject();
      var modulus = (asn1sequence.elements[1] as ASN1Integer).valueAsBigInteger;
      var exponent =
          (asn1sequence.elements[3] as ASN1Integer).valueAsBigInteger;
      var p = (asn1sequence.elements[4] as ASN1Integer).valueAsBigInteger;
      var q = (asn1sequence.elements[5] as ASN1Integer).valueAsBigInteger;
      return RSAPrivateKey(modulus, exponent, p, q);
    } catch (e) {
      print(e);
      return null;
    }
  }

List<int> decodeWithPrivKey(List<int> data, RSAPrivateKey privateKey) {
    return (RSAEngine()
          ..init(false, PrivateKeyParameter<RSAPrivateKey>(privateKey)))
        .process(Uint8List.fromList(data))
        .toList();
  }