Образец кода:

        CspParameters cspParameters = new CspParameters();
        cspParameters.ProviderType = 1; // PROV_RSA_FULL

        // Create the crypto service provider, generating a new
        // key.
        mRsaCSP = new RSACryptoServiceProvider(mDefaultKeyLength, cspParameters);
        mRsaCSP.PersistKeyInCsp = true;
        RSAParameters privateKey = mRsaCSP.ExportParameters(true);


        byte[] rsaBytes = mRsaCSP.ExportCspBlob(true);

        try
        {
            X509Certificate2 cert = new X509Certificate2(rsaBytes);                
            mKeyDataPfx = Convert.ToBase64String(cert.Export(X509ContentType.Pkcs12, password));
        }
        catch (Exception ce)
        {
            string error = ce.Message;
        }