How to change CSP parameter of RSACryptoServiceProvider

Question

I am doing rsa-sha256 xml signing using SignedXML class. But the problem is I need to change CSP to support sha256.

This is how I am selecting certificate,

public X509Certificate2 GetCertificateFromStore()
        {
            X509Store st = new X509Store(StoreName.My, StoreLocation.CurrentUser);
            st.Open(OpenFlags.ReadOnly);
            X509Certificate2Collection col = st.Certificates.Find(X509FindType.FindByTimeValid, (object)DateTime.Now, false);

            X509Certificate2 x509Certificate =null;
            X509Certificate2Collection sel = X509Certificate2UI.SelectFromCollection(col, "Certificate", "Select single certificate to sign", X509SelectionFlag.SingleSelection);
            if (sel.Count > 0)
            {
                X509Certificate2Enumerator en = sel.GetEnumerator();
                en.MoveNext();
                x509Certificate = en.Current;
            }
            st.Close();
            //x509Certificate.s
            return x509Certificate;
        }

This is how I am trying to change CSP parameter.

byte[] privateKeyBlob;
            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa = cert.PrivateKey as RSACryptoServiceProvider;
            try
            {
                privateKeyBlob = rsa.ExportCspBlob(true);
            }
            catch
            {
                throw new ApplicationException("Private key fails to export");
            }
            // To use the RSA-SHA256 the CryptoAPI needs to select a special CSP: Microsoft Enhanced RSA and AES Cryptographic Provider
            // By reinstantiating a CSP of type 24 we ensure that we get the right CSP.
            CspParameters cp = new CspParameters(24);
            rsa = new RSACryptoServiceProvider(cp);
            rsa.ImportCspBlob(privateKeyBlob);


            signer.SigningKey = rsa;
            signer.KeyInfo = getKeyInfo(signer, cert);

Problem is I am using USB device token and I doubt private key is not exportable. On exporting its throwing an error 'Key not valid for use in specified state.'.

Can anybody help how to do this?

The exception is because rsa.CspKeyContainerInfo.Exportable is false, thus, the private key cannot be exported — Suicide Platypus, Dec 21 '16 at 11:39

score 1 · Accepted Answer · answered Jul 30 '12 at 12:29

1

If any one interested here is my solution, I ended up using another new version of my 3rd party CSP. The CSP version I was using was an old one and I switched to new version. Now the signing is working. Thanks for your help.

answered Jul 30 '12 at 12:29

Matt

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How to change CSP parameter of RSACryptoServiceProvider

1 Answers1