/*
* Diffie-Hellman
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/

#ifndef BOTAN_DIFFIE_HELLMAN_H__
#define BOTAN_DIFFIE_HELLMAN_H__

#include <botan/dl_algo.h>
#include <botan/pow_mod.h>
#include <botan/blinding.h>
#include <botan/pk_ops.h>

namespace Botan {

/**
* This class represents Diffie-Hellman public keys.
*/
class BOTAN_DLL DH_PublicKey : public virtual DL_Scheme_PublicKey
   {
   public:
      std::string algo_name() const { return "DH"; }

      std::vector<byte> public_value() const;
      size_t max_input_bits() const { return group_p().bits(); }

      DL_Group::Format group_format() const { return DL_Group::ANSI_X9_42; }

      DH_PublicKey(const AlgorithmIdentifier& alg_id,
                   const secure_vector<byte>& key_bits) :
         DL_Scheme_PublicKey(alg_id, key_bits, DL_Group::ANSI_X9_42) {}

      /**
      * Construct a public key with the specified parameters.
      * @param grp the DL group to use in the key
      * @param y the public value y
      */
      DH_PublicKey(const DL_Group& grp, const BigInt& y);
   protected:
      DH_PublicKey() {}
   };

/**
* This class represents Diffie-Hellman private keys.
*/
class BOTAN_DLL DH_PrivateKey : public DH_PublicKey,
                                public PK_Key_Agreement_Key,
                                public virtual DL_Scheme_PrivateKey
   {
   public:
      std::vector<byte> public_value() const;

      /**
      * Load a DH private key
      * @param alg_id the algorithm id
      * @param key_bits the subject public key
      * @param rng a random number generator
      */
      DH_PrivateKey(const AlgorithmIdentifier& alg_id,
                    const secure_vector<byte>& key_bits,
                    RandomNumberGenerator& rng);

      /**
      * Construct a private key with predetermined value.
      * @param rng random number generator to use
      * @param grp the group to be used in the key
      * @param x the key's secret value (or if zero, generate a new key)
      */
      DH_PrivateKey(RandomNumberGenerator& rng, const DL_Group& grp,
                    const BigInt& x = 0);
   };

/**
* DH operation
*/
class BOTAN_DLL DH_KA_Operation : public PK_Ops::Key_Agreement
   {
   public:
      DH_KA_Operation(const DH_PrivateKey& key,
                      RandomNumberGenerator& rng);

      secure_vector<byte> agree(const byte w[], size_t w_len);
   private:
      const BigInt& p;

      Fixed_Exponent_Power_Mod powermod_x_p;
      Blinder blinder;
   };

}

#endif