DSA_PublicKey::create_verification_op(const std::string& params,
                                      const std::string& provider) const
   {
   if(provider == "base" || provider.empty())
      return std::unique_ptr<PK_Ops::Verification>(new DSA_Verification_Operation(*this, params));
   throw Provider_Not_Found(algo_name(), provider);
   }
DSA_PublicKey::create_verification_op(const std::string& params,
                                      const std::string& provider) const
   {
   if(provider == "base" || provider.empty())
      return std::unique_ptr<PK_Ops::Verification>(new DSA_Verification_Operation(*this, params));
   throw Provider_Not_Found(algo_name(), provider);
   }