Chilkat.PrivateKey privKey = null;
Chilkat.Cert cert = pfx.GetCert(0);
cert.ExportCertPemFile(@"C:\cert.crt");
privKey = cert.ExportPrivateKey();
privKey.SaveRsaPemFile(@"C:\rsapem.key");
privKey.SavePkcs1File(@"C:\pkcs1.key");
privKey.SavePemFile(@"C:\pem.key");
Console.WriteLine(privKey.GetRsaPem());
I noticed that SaveRsaPemFile and GetRsaPem have different outputs. The file has BEGIN PRIVATE KEY, while the GetRsaPem has BEGIN RSA PRIVATE KEY