How to create a completely new x509Certificate2 in .Net?

Question

I google it from web, find many examples to generate a new x509Certificate2 from a file in .Net, but there is no example to show how to generate a completely new x509Certificate2 from the beginning in .net.

Is there any one that can tell me how to do it in .net?

Answer 1

Checkout CertificateRequest (Name Space: System.Security.Cryptography.X509Certificates)...

 public static X509Certificate2 GenerateSelfSignedCertificate()
    {
        string secp256r1Oid = "1.2.840.10045.3.1.7";  //oid for prime256v1(7)  other identifier: secp256r1
        
        string subjectName = "Self-Signed-Cert-Example";

        var ecdsa = ECDsa.Create(ECCurve.CreateFromValue(secp256r1Oid));

        var certRequest = new CertificateRequest($"CN={subjectName}", ecdsa, HashAlgorithmName.SHA256);

        //add extensions to the request (just as an example)
        //add keyUsage
        certRequest.CertificateExtensions.Add(new X509KeyUsageExtension(X509KeyUsageFlags.DigitalSignature, true));

        X509Certificate2 generatedCert = certRequest.CreateSelfSigned(DateTimeOffset.Now.AddDays(-1), DateTimeOffset.Now.AddYears(10)); // generate the cert and sign!

        X509Certificate2 pfxGeneratedCert = new X509Certificate2(generatedCert.Export(X509ContentType.Pfx)); //has to be turned into pfx or Windows at least throws a security credentials not found during sslStream.connectAsClient or HttpClient request...

     return pfxGeneratedCert;
}