CspParameters cspparams = new CspParams { Flags = CspProviderFlags.CreateEphemeralKey };
 using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(cspparams))
{   // Both shown here but only one used depending on operation
    // For the signing RSA use this:
    rsa.ImportCspBlob(pvkBlob);
    // for the verifying RSA use this:
    rsa.ImportCspBlob(pukBlob);

    byte[] modelBlob = GetModelBlob(model);
    HashAlgorithm halgo = HashAlgorithm.Create("SHA1");

    // For signing use this:
    model.Signature = null;   // not used to compute sig
    DataContractSerializer serializer = new DataContractSerializer(model.GetType());
    using (MemoryStream memoryStream = new MemoryStream())
    {
        serializer.WriteObject(memoryStream, model);
        byte[] toSaveSig = rsa.SignData(memoryStream, halgo);
        model.Signature = toSaveSig;
    }

    // For verifying use this:
    byte[] retrievedSig = model.Signature;
    model.Signature = null;   // not used to compute sig
    bool verified = rsa.VerifyData(modelBlob, halgo, retrievedSig);
}