Próbuję podpisać plik za pomocą ECDSA za pomocą API CNG i certyfikatu z Microsoft Certificate Store. Przeczytałem wiele dokumentacji i nie tylko, ale mam problem z importowaniem klucza prywatnego z certyfikatu. Zrobiłem to samo z RSA, ale wygląda na to, że robi się to zupełnie inaczej. Oto kod, który mam do tej pory:

<code>    static void signFile()
    {
        X509Certificate2 myCert = 
             selectCert(StoreName.My, 
                        StoreLocation.CurrentUser, 
                        "Select a Certificate",
                        "Please select a certificate from the list below:");

        Console.Write("Path for file to sign: ");
        string path = Console.ReadLine();
        TextReader file = null;
        try
        {
            file = new StreamReader(path);
        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
            Console.Write("\nPress any key to return to the main menu: ");
            Console.ReadKey();
        }
        UnicodeEncoding encoding = new UnicodeEncoding();
        byte[] data = encoding.GetBytes(file.ReadToEnd());
        ECDsaCng dsa = new ECDsaCng(
            CngKey.Import(StringToByteArray(myCert.PrivateKey.ToString()),
                          CngKeyBlobFormat.EccPrivateBlob,
                          CngProvider.MicrosoftSoftwareKeyStorageProvider));

        dsa.HashAlgorithm = CngAlgorithm.Sha384;
        byte[] sig = dsa.SignData(data);
        TextWriter signatureFile = new StreamWriter("signature.txt");
        signatureFile.WriteLine("-----BEGIN SHA384 SIGNATURE-----" + 
                                ByteArrayToString(sig) + 
                                "-----END SHA384 SIGNATURE-----");
        signatureFile.Close();
    }
</code>

I dostaję błąd

System.NotSupportedException: Algorytm klucza certyfikatu nie jest obsługiwany.

Mój certyfikat to ECDSA_P256 sha384ECDSA z następującymi rozszerzeniami:

<code>Digital Signature, Non-repudiation, independent signing revocation list (CRL), CRL Signing (CRL) (c2)
Server Authentication (1.3.6.1.5.5.7.3.1)
Client Authentication (1.3.6.1.5.5.7.3.2)
Code Signing (1.3.6.1.5.5.7.3.3)
Unknown Key Usage (1.3.6.1.4.1.311.2.1.22)
Unknown Key Usage (1.3.6.1.4.1.311.2.1.21)
IKE-intermediary IP-security (1.3.6.1.5.5.8.2.2)
</code>

Wydawałoby się, że problem stanowi certyfikat, ale nie jestem pewien, czy może to być kod, czy nie.

Oto mój certyfikat z kluczem publicznym:

<code>Certificate:
Data:
    Version: 3 (0x2)
    Serial Number: 2 (0x2)
Signature Algorithm: ecdsa-with-SHA384
    Issuer: C=##, O=#######, OU=#####, OU=#####, CN=###########
    Validity
        Not Before: Apr 27 16:35:51 2012 GMT
        Not After : Apr 26 16:35:51 2017 GMT
    Subject: C=##, O=###########, OU=#####, CN=#############
    Subject Public Key Info:
        Public Key Algorithm: id-ecPublicKey
            Public-Key: (256 bit)
            pub:
                04:fc:d5:ce:ad:1f:0c:19:b9:3d:2b:bd:7d:f0:8c:
                44:46:db:e3:42:14:b1:1a:9f:7c:ab:e1:be:ad:a5:
                0c:03:2d:0f:ff:3f:10:d4:69:eb:4c:82:a1:2a:61:
                56:45:03:04:a6:49:f7:16:6e:dd:60:22:c6:20:c5:
                4d:44:49:21:41
            ASN1 OID: prime256v1
    X509v3 extensions:
        X509v3 Key Usage: critical
            Digital Signature, Non Repudiation, CRL Sign
        X509v3 Extended Key Usage: critical
            TLS Web Server Authentication, TLS Web Client Authentication, Co
de Signing, Microsoft Commercial Code Signing, Microsoft Individual Code Signing
, 1.3.6.1.5.5.8.2.2
        X509v3 Authority Key Identifier:
            DirName:/C=##/O=#######/OU=#####/OU=#####/CN=######
            serial:01
        X509v3 Subject Key Identifier:
            B7:A8:F9:55:9A:43:9E:BE:1C:4B:62:52:91:C2:F1:39:72:E1:CE:1B
        X509v3 Basic Constraints: critical
            CA:FALSE
Signature Algorithm: ecdsa-with-SHA384
     30:81:88:02:42:01:75:55:f3:64:f9:aa:2a:66:55:b1:ca:dc:
     86:ac:1f:7d:2a:ec:10:87:db:74:88:0e:77:e3:18:82:15:a7:
     32:91:1a:2d:ea:07:2e:78:8d:dc:8a:18:3c:2b:5a:9b:6a:0f:
     97:f6:f8:8d:c5:fc:0e:9f:20:e9:b0:16:90:1a:c4:58:ac:02:
     42:01:dc:b3:88:ae:44:54:c4:e0:b7:c2:37:88:0b:19:6b:96:
     99:f7:21:12:45:12:21:e5:ab:83:39:a6:47:3a:08:87:b0:fa:
     0e:31:1b:97:83:8d:65:30:a1:43:c1:82:27:77:6e:93:89:1b:
     bd:57:b1:7a:54:9e:cc:e1:44:cc:74:16:c5
</code>