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c#smartcarddigitalgemalto

Smart Card gives null as a value of private key

I am using a Gemalto Smart card to sign XML documents.

I have a method which returns the certificate and searches by the thumbprint that is hard coded.

I am unable to obtain the private key from that Smart card and sign the doc with it.

It returns null when I debug the app.

My goal is to get the private key and then ask the user for the PIN to authorize the signing of the document.

    public static X509Certificate2 GetDefaultCertificateStoredOnTheCard()
    {
        X509Store store = new X509Store("MY", StoreLocation.LocalMachine);
        store.Open(OpenFlags.ReadOnly | OpenFlags.OpenExistingOnly);
        X509Certificate2Collection certs = store.Certificates.Find(X509FindType.FindByTimeValid, DateTime.Now, true);

        // by thumbprint, there is only one
        certs = certs.Find(X509FindType.FindByThumbprint, "6BB4F9D483206F44A992799541114536579CF2B3", true);

        if (certs.Count == 0)
        {
            throw new ArgumentException("Please insert smart card to obtain certificate.");
        }
        X509Certificate2 cert = certs[0];

        RSACryptoServiceProvider key;

        if (cert.HasPrivateKey)
        {
            // software cert
            key = cert.PrivateKey as RSACryptoServiceProvider;

        }
        else
        {
            // certificate from smartcard
            CspParameters csp = new CspParameters(1, "Microsoft Base Smart Card Crypto Provider");
            csp.Flags = CspProviderFlags.UseDefaultKeyContainer;
            key = new RSACryptoServiceProvider(csp);
        }

        return cert;
    }

As you can see if the key is null, set the key to use the Microsoft Base Smart Card Crypto Provider.

I have noticed on device manager that my Smart Card Reader is Microsoft Usbccid Smartcard Reader.

Not sure if I should set something else here , it brings this window and an error with it.

enter image description here

Solution

  • The very purpose of a smart card is to protect confidential data. There are no more confidential data than the private key (often this never leaves the smart card), so it is a sign of correct functioning, that you don't get it.

    Actually you have to let the smart card do the signature, probably by sending the hash value of your XML document.