BouncyCastle RSAPrivateKey to .NET RSAPrivateKey

Question

I'm creating a certificate distribution system to keep track of clients and stuff.

What happens is:

• Client send CSR to Server
• Server checks and signs certificate
• Server sends Signed certificate to Client
• Client puts Signed certificate plus Private key in Windows store.

So on the client this happens:

//Pseudo Server Object:
Server s = new Server();  

//Requested Certificate Name and things
X509Name name = new X509Name("CN=Client Cert, C=NL");  

//Key generation 2048bits
RsaKeyPairGenerator rkpg = new RsaKeyPairGenerator();
rkpg.Init(new KeyGenerationParameters(new SecureRandom(), 2048));
AsymmetricCipherKeyPair ackp = rkpg.GenerateKeyPair();  

//PKCS #10 Certificate Signing Request
Pkcs10CertificationRequest csr = new Pkcs10CertificationRequest("SHA1WITHRSA", name, ackp.Public, null, ackp.Private);  

//Make it a nice PEM thingie
StringBuilder sb = new StringBuilder();
PemWriter pemwrit = new PemWriter(new StringWriter(b));
pemwrit.WriteObject(csr);
pemwrit.Writer.Flush();
s.SendRequest(sb.ToSting());

Ok So I'll skip serverside Just trust me the server signs the cert and send it back to the client. Thats where I'll pick up the action.

PemReader pr = new PemReader(new StringReader(b.ToString()));
X509Certificate cert = (X509Certificate)pr.ReadObject();  

//So lets asume I saved the AsymmetricCipherKeyPair (ackp) from before
//I have now the certificate and my private key;

//first I make it a "Microsoft" x509cert.
//This however does not have a PrivateKey thats in the AsymmetricCipherKeyPair (ackp)
System.Security.Cryptography.X509Certificates.X509Certificate2 netcert = DotNetUtilities.ToX509Certificate(cert);

//So here comes the RSACryptoServerProvider:
System.Security.Cryptography.RSACryptoServiceProvider rcsp = new System.Security.Cryptography.RSACryptoServiceProvider();  

//And the privateKeyParameters
System.Security.Cryptography.RSAParameters parms = new System.Security.Cryptography.RSAParameters();  

//now I have to translate ackp.PrivateKey to parms;
RsaPrivateCrtKeyParameters BCKeyParms = ((RsaPrivateCrtKeyParameters)ackp1.Private);  

//D is the private exponent
parms.Modulus   = BCKeyParms.Modulus.ToByteArray();
parms.P         = BCKeyParms.P.ToByteArray();
parms.Q         = BCKeyParms.Q.ToByteArray();
parms.DP        = BCKeyParms.DP.ToByteArray();
parms.DQ        = BCKeyParms.DQ.ToByteArray();
parms.InverseQ  = BCKeyParms.QInv.ToByteArray();
parms.D         = BCKeyParms.Exponent.ToByteArray();
parms.Exponent  = BCKeyParms.PublicExponent.ToByteArray();  

//Now I should be able to import the RSAParameters into the RSACryptoServiceProvider
rcsp.ImportParameters(parms);  

//<em><b>not really</b></em> This breaks says "Bad Data" and not much more. I'll Post the 
//stacktrace at the end  

//I open up the windows cert store because thats where I want to save it.
//Add it and save it this works fine without the privkey.
X509Store store = new X509Store(StoreName.My, StoreLocation.CurrentUser);
store.Open(OpenFlags.MaxAllowed);
store.Add(netcert);
store.Close();

Now you're probably thinking there must be something going wrong at the server side. Well thats what I thought too but When I made a pfx file from this cert and imported it by hand it worked fine ....

Somehow there's a diference bewteen a .NET RSA privatekey and a BouncyCastle RSA privatekey and I can't put my finger on it.

You will probably suggest to import the pfx and then get the private key from it via the X509Store. I tried. :S And failed. As soon as I try to ExportParameters(true) the true stands for including privateparameters. It says "Key not valid for use in specified state.". See for complete exception at the end.

I hope some of you have slain this pig before or might be able to help me.

***Exceptions:***

System.Security.Cryptography.CryptographicException was unhandled
  Message="Key not valid for use in specified state.\r\n"
  Source="mscorlib"
  StackTrace:
       at System.Security.Cryptography.CryptographicException.ThrowCryptogaphicException(Int32 hr)
       at System.Security.Cryptography.Utils._ExportKey(SafeKeyHandle hKey, Int32 blobType, Object cspObject)
       at System.Security.Cryptography.RSACryptoServiceProvider.ExportParameters(Boolean includePrivateParameters)
  InnerException: 

***And the other one:***

System.Security.Cryptography.CryptographicException was unhandled
  Message="Bad Data.\r\n"
  Source="mscorlib"
  StackTrace:
       at System.Security.Cryptography.CryptographicException.ThrowCryptogaphicException(Int32 hr)
       at System.Security.Cryptography.Utils._ImportKey(SafeProvHandle hCSP, Int32 keyNumber, CspProviderFlags flags, Object cspObject, SafeKeyHandle& hKey)
       at System.Security.Cryptography.RSACryptoServiceProvider.ImportParameters(RSAParameters parameters)
  InnerException: 

Answer 1

FYI, I've added this functionality to the Org.BouncyCastle.Security.DotNetUtilities class; it will be in release 1.6, due soon.