Certificate generation with BouncyCastle C#

cert.cs

using Org.BouncyCastle.Asn1.Pkcs;
using Org.BouncyCastle.Asn1.Sec;
using Org.BouncyCastle.Asn1.X509;
using Org.BouncyCastle.Asn1.X9;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Generators;
using Org.BouncyCastle.Crypto.Operators;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.X509;
using System;
using System.IO;

class Program
{
    static SecureRandom secureRandom = new SecureRandom();

    static AsymmetricCipherKeyPair GenerateRsaKeyPair(int length)
    {
        var keygenParam = new KeyGenerationParameters(secureRandom, length);

        var keyGenerator = new RsaKeyPairGenerator();
        keyGenerator.Init(keygenParam);
        return keyGenerator.GenerateKeyPair();
    }

    static AsymmetricCipherKeyPair GenerateEcKeyPair(string curveName)
    {
        var ecParam = SecNamedCurves.GetByName(curveName);
        var ecDomain = new ECDomainParameters(ecParam.Curve, ecParam.G, ecParam.N);
        var keygenParam = new ECKeyGenerationParameters(ecDomain, secureRandom);

        var keyGenerator = new ECKeyPairGenerator();
        keyGenerator.Init(keygenParam);
        return keyGenerator.GenerateKeyPair();
    }

    static X509Certificate GenerateCertificate(
        X509Name issuer, X509Name subject,
        AsymmetricKeyParameter issuerPrivate,
        AsymmetricKeyParameter subjectPublic)
    {
        ISignatureFactory signatureFactory;
        if (issuerPrivate is ECPrivateKeyParameters)
        {
            signatureFactory = new Asn1SignatureFactory(
                X9ObjectIdentifiers.ECDsaWithSha256.ToString(),
                issuerPrivate);
        }
        else
        {
            signatureFactory = new Asn1SignatureFactory(
                PkcsObjectIdentifiers.Sha256WithRsaEncryption.ToString(),
                issuerPrivate);
        }

        var certGenerator = new X509V3CertificateGenerator();
        certGenerator.SetIssuerDN(issuer);
        certGenerator.SetSubjectDN(subject);
        certGenerator.SetSerialNumber(BigInteger.ValueOf(1));
        certGenerator.SetNotAfter(DateTime.UtcNow.AddHours(1));
        certGenerator.SetNotBefore(DateTime.UtcNow);
        certGenerator.SetPublicKey(subjectPublic);
        return certGenerator.Generate(signatureFactory);
    }

    static bool ValidateSelfSignedCert(X509Certificate cert, ICipherParameters pubKey)
    {
        cert.CheckValidity(DateTime.UtcNow);
        var tbsCert = cert.GetTbsCertificate();
        var sig = cert.GetSignature();

        var signer = SignerUtilities.GetSigner(cert.SigAlgName);
        signer.Init(false, pubKey);
        signer.BlockUpdate(tbsCert, 0, tbsCert.Length);
        return signer.VerifySignature(sig);
    }

    static void Main(string[] args)
    {
        var caName = new X509Name("CN=TestCA");
        var eeName = new X509Name("CN=TestEE");
        var caKey = GenerateEcKeyPair("secp256r1");
        var eeKey = GenerateRsaKeyPair(2048);

        var caCert = GenerateCertificate(caName, caName, caKey.Private, caKey.Public);
        var eeCert = GenerateCertificate(caName, eeName, caKey.Private, eeKey.Public);
        var caOk = ValidateSelfSignedCert(caCert, caKey.Public);
        var eeOk = ValidateSelfSignedCert(eeCert, caKey.Public);

        using (var f = File.OpenWrite("ca.cer"))
        {
            var buf = caCert.GetEncoded();
            f.Write(buf, 0, buf.Length);
        }

        using (var f = File.OpenWrite("ee.cer"))
        {
            var buf = eeCert.GetEncoded();
            f.Write(buf, 0, buf.Length);
        }
    }
}

Sorry this code does not write the private key output to files. It will be stored in caKey and eeKey. If you want to write pfx to file, you'll need to use Pkcs12Store and give the password to Save method.