ecdh.h

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/*
* ECDH
* (C) 2007 Falko Strenzke, FlexSecure GmbH
*          Manuel Hartl, FlexSecure GmbH
* (C) 2008-2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/

#ifndef BOTAN_ECDH_KEY_H__
#define BOTAN_ECDH_KEY_H__

#include <botan/ecc_key.h>
#include <botan/pk_ops.h>

namespace Botan {

/**
* This class represents ECDH Public Keys.
*/
class BOTAN_DLL ECDH_PublicKey : public virtual EC_PublicKey
   {
   public:

      ECDH_PublicKey(const AlgorithmIdentifier& alg_id,
                     const secure_vector<byte>& key_bits) :
         EC_PublicKey(alg_id, key_bits) {}

      /**
      * Construct a public key from a given public point.
      * @param dom_par the domain parameters associated with this key
      * @param public_point the public point defining this key
      */
      ECDH_PublicKey(const EC_Group& dom_par,
                     const PointGFp& public_point) :
         EC_PublicKey(dom_par, public_point) {}

      /**
      * Get this keys algorithm name.
      * @return this keys algorithm name
      */
      std::string algo_name() const { return "ECDH"; }

      /**
      * Get the maximum number of bits allowed to be fed to this key.
      * This is the bitlength of the order of the base point.

      * @return maximum number of input bits
      */
      size_t max_input_bits() const { return domain().get_order().bits(); }

      /**
      * @return public point value
      */
      std::vector<byte> public_value() const
         { return unlock(EC2OSP(public_point(), PointGFp::UNCOMPRESSED)); }

   protected:
      ECDH_PublicKey() {}
   };

/**
* This class represents ECDH Private Keys.
*/
class BOTAN_DLL ECDH_PrivateKey : public ECDH_PublicKey,
                                  public EC_PrivateKey,
                                  public PK_Key_Agreement_Key
   {
   public:

      ECDH_PrivateKey(const AlgorithmIdentifier& alg_id,
                      const secure_vector<byte>& key_bits) :
         EC_PrivateKey(alg_id, key_bits) {}

      /**
      * Generate a new private key
      * @param rng a random number generator
      * @param domain parameters to used for this key
      * @param x the private key; if zero, a new random key is generated
      */
      ECDH_PrivateKey(RandomNumberGenerator& rng,
                      const EC_Group& domain,
                      const BigInt& x = 0) :
         EC_PrivateKey(rng, domain, x) {}

      std::vector<byte> public_value() const
         { return ECDH_PublicKey::public_value(); }
   };

/**
* ECDH operation
*/
class BOTAN_DLL ECDH_KA_Operation : public PK_Ops::Key_Agreement
   {
   public:
      ECDH_KA_Operation(const ECDH_PrivateKey& key);

      secure_vector<byte> agree(const byte w[], size_t w_len);
   private:
      const CurveGFp& curve;
      const BigInt& cofactor;
      BigInt l_times_priv;
   };

}

#endif