Bouncy Castle's X509V3CertificateGenerator.SetSignatureAlgorithm marked obsolete. What do I do?

Question

I am trying to create a self-signed trusted certificate. I am using Bouncy Castle from nuget, and the answer on this question. This is the code on that page:

Answer 1

To make IdahoSixString's excellent answer more complete: The above code will not work in the part where it tries to bind the certificate to the program and port:

('netsh http add sslcert ipport=0.0.0.0:4443 certhash={certificate.Thumbprint} appid={{{applicationId}}}'). At least not in .NET4.5. 

You will get the error:

"SSL Certificate add failed, Error: 1312 A specified logon session does not exist. It may already have been terminated."

This is apparently because the private key does not persist when the corresponding RSA object is closed. So I followed the advise in this link, and the following code works for me:

public static X509Certificate2 CreateSelfSignedCertificateBasedOnCertificateAuthorityPrivateKey(string subjectName, string issuerName, AsymmetricKeyParameter issuerPrivKey)
    {
        const int keyStrength = 2048;

        // Generating Random Numbers
        CryptoApiRandomGenerator randomGenerator = new CryptoApiRandomGenerator();
        SecureRandom random = new SecureRandom(randomGenerator);
        ISignatureFactory signatureFactory = new Asn1SignatureFactory("SHA512WITHRSA", issuerPrivKey, random);

        // The Certificate Generator
        X509V3CertificateGenerator certificateGenerator = new X509V3CertificateGenerator();
        certificateGenerator.AddExtension(X509Extensions.ExtendedKeyUsage.Id, true, new ExtendedKeyUsage(KeyPurposeID.IdKPServerAuth));

        // Serial Number
        BigInteger serialNumber = BigIntegers.CreateRandomInRange(BigInteger.One, BigInteger.ValueOf(Int64.MaxValue), random);
        certificateGenerator.SetSerialNumber(serialNumber);

        // Issuer and Subject Name
        X509Name subjectDN = new X509Name("CN=" + subjectName);
        X509Name issuerDN = new X509Name("CN=" + issuerName);
        certificateGenerator.SetIssuerDN(issuerDN);
        certificateGenerator.SetSubjectDN(subjectDN);

        // Valid For
        DateTime notBefore = DateTime.UtcNow.Date;
        DateTime notAfter = notBefore.AddYears(2);
        certificateGenerator.SetNotBefore(notBefore);
        certificateGenerator.SetNotAfter(notAfter);

        // Subject Public Key
        AsymmetricCipherKeyPair subjectKeyPair;
        var keyGenerationParameters = new KeyGenerationParameters(random, keyStrength);
        var keyPairGenerator = new RsaKeyPairGenerator();
        keyPairGenerator.Init(keyGenerationParameters);
        subjectKeyPair = keyPairGenerator.GenerateKeyPair();

        certificateGenerator.SetPublicKey(subjectKeyPair.Public);

        // selfsign certificate
        Org.BouncyCastle.X509.X509Certificate certificate = certificateGenerator.Generate(signatureFactory);
        var dotNetPrivateKey = ToDotNetKey((RsaPrivateCrtKeyParameters)subjectKeyPair.Private);

        // merge into X509Certificate2
        X509Certificate2 x509 = new X509Certificate2(DotNetUtilities.ToX509Certificate(certificate));
        x509.PrivateKey = dotNetPrivateKey;
        x509.FriendlyName = subjectName;

        return x509;
    }

    public static X509Certificate2 CreateCertificateAuthorityCertificate(string subjectName, out AsymmetricKeyParameter CaPrivateKey)
    {
        const int keyStrength = 2048;

        // Generating Random Numbers
        CryptoApiRandomGenerator randomGenerator = new CryptoApiRandomGenerator();
        SecureRandom random = new SecureRandom(randomGenerator);

        // The Certificate Generator
        X509V3CertificateGenerator certificateGenerator = new X509V3CertificateGenerator();

        // Serial Number
        BigInteger serialNumber = BigIntegers.CreateRandomInRange(BigInteger.One, BigInteger.ValueOf(Int64.MaxValue), random);
        certificateGenerator.SetSerialNumber(serialNumber);

        // Issuer and Subject Name
        X509Name subjectDN = new X509Name("CN=" + subjectName);
        X509Name issuerDN = subjectDN;
        certificateGenerator.SetIssuerDN(issuerDN);
        certificateGenerator.SetSubjectDN(subjectDN);

        // Valid For
        DateTime notBefore = DateTime.UtcNow.Date;
        DateTime notAfter = notBefore.AddYears(2);

        certificateGenerator.SetNotBefore(notBefore);
        certificateGenerator.SetNotAfter(notAfter);

        // Subject Public Key
        AsymmetricCipherKeyPair subjectKeyPair;
        KeyGenerationParameters keyGenerationParameters = new KeyGenerationParameters(random, keyStrength);
        RsaKeyPairGenerator keyPairGenerator = new RsaKeyPairGenerator();
        keyPairGenerator.Init(keyGenerationParameters);
        subjectKeyPair = keyPairGenerator.GenerateKeyPair();

        certificateGenerator.SetPublicKey(subjectKeyPair.Public);

        // Generating the Certificate
        AsymmetricCipherKeyPair issuerKeyPair = subjectKeyPair;
        ISignatureFactory signatureFactory = new Asn1SignatureFactory("SHA512WITHRSA", issuerKeyPair.Private, random);

        // selfsign certificate
        Org.BouncyCastle.X509.X509Certificate certificate = certificateGenerator.Generate(signatureFactory);

        X509Certificate2 x509 = new X509Certificate2(certificate.GetEncoded());
        x509.FriendlyName = subjectName;

        CaPrivateKey = issuerKeyPair.Private;

        return x509;
    }

    public static AsymmetricAlgorithm ToDotNetKey(RsaPrivateCrtKeyParameters privateKey)
    {
        var cspParams = new CspParameters()
        {
            KeyContainerName = Guid.NewGuid().ToString(),
            KeyNumber = (int)KeyNumber.Exchange,
            Flags = CspProviderFlags.UseMachineKeyStore
        };

        var rsaProvider = new RSACryptoServiceProvider(cspParams);
        var parameters = new RSAParameters()
        {
            Modulus = privateKey.Modulus.ToByteArrayUnsigned(),
            P = privateKey.P.ToByteArrayUnsigned(),
            Q = privateKey.Q.ToByteArrayUnsigned(),
            DP = privateKey.DP.ToByteArrayUnsigned(),
            DQ = privateKey.DQ.ToByteArrayUnsigned(),
            InverseQ = privateKey.QInv.ToByteArrayUnsigned(),
            D = privateKey.Exponent.ToByteArrayUnsigned(),
            Exponent = privateKey.PublicExponent.ToByteArrayUnsigned()
        };

        rsaProvider.ImportParameters(parameters);
        return rsaProvider;
    }