/*

* ECDH implemenation

* (C) 2007 Manuel Hartl, FlexSecure GmbH

*     2007 Falko Strenzke, FlexSecure GmbH

*     2008-2010 Jack Lloyd

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#include <botan/ecdh.h>

#include <botan/numthry.h>

#include <botan/internal/pk_ops_impl.h>

#if defined(BOTAN_HAS_OPENSSL)

  #include <botan/internal/openssl.h>

#endif

namespace Botan {

std::unique_ptr<Public_Key> ECDH_PrivateKey::public_key() const

   {

   return std::unique_ptr<Public_Key>(new ECDH_PublicKey(domain(), public_point()));

   }

namespace {

/**

* ECDH operation

*/

class ECDH_KA_Operation final : public PK_Ops::Key_Agreement_with_KDF

   {

   public:

      ECDH_KA_Operation(const ECDH_PrivateKey& key, const std::string& kdf, RandomNumberGenerator& rng) :

         PK_Ops::Key_Agreement_with_KDF(kdf),

         m_group(key.domain()),

         m_rng(rng)

         {

         m_l_times_priv = m_group.inverse_mod_order(m_group.get_cofactor()) * key.private_value();

         }

      size_t agreed_value_size() const override { return m_group.get_p_bytes(); }

      secure_vector<uint8_t> raw_agree(const uint8_t w[], size_t w_len) override

         {

         PointGFp input_point = m_group.get_cofactor() * m_group.OS2ECP(w, w_len);

         input_point.randomize_repr(m_rng);

         const PointGFp S = m_group.blinded_var_point_multiply(

            input_point, m_l_times_priv, m_rng, m_ws);

         if(S.on_the_curve() == false)

            throw Internal_Error("ECDH agreed value was not on the curve");

         return BigInt::encode_1363(S.get_affine_x(), m_group.get_p_bytes());

         }

   private:

      const EC_Group m_group;

      BigInt m_l_times_priv;

      RandomNumberGenerator& m_rng;

      std::vector<BigInt> m_ws;

   };

}

std::unique_ptr<PK_Ops::Key_Agreement>

ECDH_PrivateKey::create_key_agreement_op(RandomNumberGenerator& rng,

                                         const std::string& params,

                                         const std::string& provider) const

   {

#if defined(BOTAN_HAS_OPENSSL)

   if(provider == "openssl" || provider.empty())

      {

      try

         {

         return make_openssl_ecdh_ka_op(*this, params);

         }

      catch(Lookup_Error&)

         {

         if(provider == "openssl")

            throw;

         }

      }

#endif

   if(provider == "base" || provider.empty())

      return std::unique_ptr<PK_Ops::Key_Agreement>(new ECDH_KA_Operation(*this, params, rng));

   throw Provider_Not_Found(algo_name(), provider);

   }

}