void SaveKey(const RSA::PrivateKey& PrivateKey, const string& filename)
{
  // DER Encode Key - PKCS #8 key format
  PrivateKey.Save(
                  FileSink(filename.c_str(), true /*binary*/).Ref()
                  );
}
void SaveKey(const RSA::PublicKey& PublicKey, const string& filename)
{
  // DER Encode Key - X.509 key format
  PublicKey.Save(
                 FileSink(filename.c_str(), true /*binary*/).Ref()
                 );
}