wiselib.testing/algorithms/crypto/ecdhfp.h

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/***************************************************************************
 ** This file is part of the generic algorithm library Wiselib.           **
 ** Copyright (C) 2008,2009 by the Wisebed (www.wisebed.eu) project.      **
 **                                                                       **
 ** The Wiselib is free software: you can redistribute it and/or modify   **
 ** it under the terms of the GNU Lesser General Public License as        **
 ** published by the Free Software Foundation, either version 3 of the    **
 ** License, or (at your option) any later version.                       **
 **                                                                       **
 ** The Wiselib is distributed in the hope that it will be useful,        **
 ** but WITHOUT ANY WARRANTY; without even the implied warranty of        **
 ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         **
 ** GNU Lesser General Public License for more details.                   **
 **                                                                       **
 ** You should have received a copy of the GNU Lesser General Public      **
 ** License along with the Wiselib.                                       **
 ** If not, see <http://www.gnu.org/licenses/>.                           **
 ***************************************************************************/

#ifndef __ALGORITHMS_CRYPTO_ECDH_H_
#define __ALGORITHMS_CRYPTO_ECDH_H_

#include "algorithms/crypto/eccfp.h"
#include "algorithms/crypto/sha1.h"
#include <string.h>

namespace wiselib
{
template<typename OsModel_P>
   class ECDH
   {
   public:
      typedef OsModel_P OsModel;

      ECDH();
      ~ECDH();

      void enable( void );
      void disable( void );

      int8_t gen_shared_secret(uint8_t *sharedkey, uint8_t key_length, NN_DIGIT *PrivateKey, Point *PublicKey);

   private:
      //objects for necessary classes
      ECCFP eccfp;
      PMP pmp;
   };

   // -----------------------------------------------------------------------
   template<typename OsModel_P>
   ECDH<OsModel_P>::
	ECDH()
   {}
   // -----------------------------------------------------------------------
   template<typename OsModel_P>
   ECDH<OsModel_P>::
	~ECDH()
   {}
   // -----------------------------------------------------------------------
   template<typename OsModel_P>
   void
   ECDH<OsModel_P>::
	enable( void )
   {
   }
   // -----------------------------------------------------------------------
   template<typename OsModel_P>
   void
   ECDH<OsModel_P>::
	disable( void )
   {
      
   }
   //----------------------------------------------------------------------------
   template<typename OsModel_P>
   int8_t
   ECDH<OsModel_P>::
	gen_shared_secret(uint8_t *sharedkey, uint8_t key_length, NN_DIGIT *PrivateKey, Point *PublicKey )
   {
      //point that consists the shared point
      Point SharedSecret;
      eccfp.p_clear(&SharedSecret);
      uint8_t z[KEYDIGITS*NN_DIGIT_LEN];

      //Alice multiplies Bob's public key with her private key
      //to generate shared secret
      eccfp.c_mul(&SharedSecret, PublicKey, PrivateKey);

      //if SharedSecret = O, return 0 --> invalid
      if (pmp.Zero(SharedSecret.x, NUMWORDS) && pmp.Zero(SharedSecret.y, NUMWORDS))
      {
         return 0;
      }
      else
      {
         // convert x coordinate to octet string Z
         pmp.Encode(z, KEYDIGITS * NN_DIGIT_LEN, SharedSecret.x, NUMWORDS);

         // use KDF to derive a shared key of length key_length
         SHA1::KDF(sharedkey, key_length, z);

         //return success
         return 1;
      }
   }
   //------------------------------------------------------------------------------
      
} //end of wiselib namespace

#endif