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CombinatoricSplitting.h

/*
 * Copyright 2003 Michael A. Marsh, Cornell University. All rights reserved.
 * This software is released under the modified BSD license.
 * See the file LICENSE in the top-level directory for details.
 */
//
// $Id: CombinatoricSplitting.h,v 1.3 2004/05/19 15:57:00 mmarsh Exp $
//
// $Log: CombinatoricSplitting.h,v $
// Revision 1.3  2004/05/19 15:57:00  mmarsh
// *** empty log message ***
//
// Revision 1.2  2003/11/04 22:23:07  mmarsh
// General code cleanup.
//
//

#ifndef __CODEX_VSS_COMBINATORICSPLITTING_H__
#define __CODEX_VSS_COMBINATORICSPLITTING_H__

#include "CODEX_ASN1/SecureBigNumber.h"
#include "CODEX_Exceptions/BignumExceptions.h"

namespace CODEX_VSS
{
   template< unsigned int NShares >
   class CombinatoricSplitting
   {
      public :
         CombinatoricSplitting( const CODEX_ASN1::BigNumber& minVal,
                                const CODEX_ASN1::BigNumber& maxVal,
                                const CODEX_ASN1::SecureBigNumber& secret );

         CombinatoricSplitting( const CODEX_ASN1::BigNumber& maxVal,
                                const CODEX_ASN1::SecureBigNumber& secret );

         virtual ~CombinatoricSplitting();

         const CODEX_ASN1::SecureBigNumber& share( unsigned int i ) const;

      private :
         CODEX_ASN1::SecureBigNumber  m_shares[ NShares ];
   };

   template< unsigned int NShares >
   CombinatoricSplitting< NShares >::CombinatoricSplitting(
      const CODEX_ASN1::BigNumber& minVal,
      const CODEX_ASN1::BigNumber& maxVal,
      const CODEX_ASN1::SecureBigNumber& secret )
   {
      BIGNUM * m = 0;
      BIGNUM * temp = 0;
      BIGNUM * total = 0;
      BIGNUM * remainder = 0;
      try
      {
         m = BN_new();
         if ( 0 == m )
         {
            throw CODEX_Exceptions::BignumNullException( __FILE__ , __LINE__ );
         }
         total = BN_new();
         if ( 0 == total )
         {
            throw CODEX_Exceptions::BignumNullException( __FILE__ , __LINE__ );
         }
         remainder = BN_new();
         if ( 0 == remainder )
         {
            throw CODEX_Exceptions::BignumNullException( __FILE__ , __LINE__ );
         } 

         if ( ! BN_sub( m, maxVal.value(), minVal.value() ) )
         {
            throw CODEX_Exceptions::BignumSubException( __FILE__ , __LINE__ );
         }
         if ( ! BN_add( m, m, BN_value_one() ) )
         {
            throw CODEX_Exceptions::BignumAddException( __FILE__ , __LINE__ );
         }

         for ( unsigned int i = 0 ; i < NShares - 1 ; ++i )
         {
            temp = BN_new();
            if ( 0 == temp )
            {
               throw CODEX_Exceptions::BignumNullException( __FILE__ ,
                                                            __LINE__ );
            }
            if ( ! BN_rand_range( temp, m ) )
            {
               throw CODEX_Exceptions::BignumRandRangeException( __FILE__ ,
                                                                 __LINE__ );
            }
            if ( ! BN_add( temp, temp, minVal.value() ) )
            {
               throw CODEX_Exceptions::BignumAddException( __FILE__ ,
                                                           __LINE__ );
            }

            if ( ! BN_add( total, total, temp ) )
            {
               throw CODEX_Exceptions::BignumAddException( __FILE__ ,
                                                           __LINE__ );
            }
            m_shares[i] = CODEX_ASN1::SecureBigNumber( temp );
            temp = 0;
         }

         if ( ! BN_sub( remainder, secret.value(), total ) )
         {
            throw CODEX_Exceptions::BignumSubException( __FILE__ , __LINE__ );
         }
         m_shares[NShares-1] = CODEX_ASN1::SecureBigNumber( remainder );
         BN_free(m);
      }
      catch ( ... )
      {
         if ( 0 != m ) BN_free(m);
         if ( 0 != temp ) BN_clear_free(temp);
         if ( 0 != total ) BN_clear_free(total);
         if ( 0 != remainder ) BN_clear_free(remainder);
         throw;
      }
   }

   template< unsigned int NShares >
   CombinatoricSplitting< NShares >::CombinatoricSplitting(
      const CODEX_ASN1::BigNumber& maxVal,
      const CODEX_ASN1::SecureBigNumber& secret )
   {
      BIGNUM * m = 0;
      BIGNUM * temp = 0;
      BIGNUM * total = 0;
      BIGNUM * remainder = 0;
      try
      {
         m = BN_new();
         if ( 0 == m )
         {
            throw CODEX_Exceptions::BignumNullException( __FILE__ , __LINE__ );
         }
         total = BN_new();
         if ( 0 == total )
         {
            throw CODEX_Exceptions::BignumNullException( __FILE__ , __LINE__ );
         }
         remainder = BN_new();
         if ( 0 == remainder )
         {
            throw CODEX_Exceptions::BignumNullException( __FILE__ , __LINE__ );
         } 

         if ( ! BN_add( m, maxVal.value(), BN_value_one() ) )
         {
            throw CODEX_Exceptions::BignumAddException( __FILE__ , __LINE__ );
         }

         for ( unsigned int i = 0 ; i < NShares - 1 ; ++i )
         {
            temp = BN_new();
            if ( 0 == temp )
            {
               throw CODEX_Exceptions::BignumNullException( __FILE__ ,
                                                            __LINE__ );
            }
            if ( ! BN_rand_range( temp, m ) )
            {
               throw CODEX_Exceptions::BignumRandRangeException( __FILE__ ,
                                                                 __LINE__ );
            }

            if ( ! BN_add( total, total, temp ) )
            {
               throw CODEX_Exceptions::BignumAddException( __FILE__ ,
                                                           __LINE__ );
            }
            m_shares[i] = CODEX_ASN1::SecureBigNumber( temp );
            temp = 0;
         }

         if ( ! BN_sub( remainder, secret.value(), total ) )
         {
            throw CODEX_Exceptions::BignumSubException( __FILE__ , __LINE__ );
         }
         m_shares[NShares-1] = CODEX_ASN1::SecureBigNumber( remainder );
         BN_free(m);
      }
      catch ( ... )
      {
         if ( 0 != m ) BN_free(m);
         if ( 0 != temp ) BN_clear_free(temp);
         if ( 0 != total ) BN_clear_free(total);
         if ( 0 != remainder ) BN_clear_free(remainder);
         throw;
      }
   }

   template< unsigned int NShares >
   CombinatoricSplitting< NShares >::~CombinatoricSplitting()
   {
   }

   template< unsigned int NShares >
   const CODEX_ASN1::SecureBigNumber&
   CombinatoricSplitting< NShares >::share( unsigned int i ) const
   {
      if ( i >= NShares )
      {
         throw CODEX_Exceptions::IllegalIndexException( __FILE__ , __LINE__ );
      }
      return m_shares[ i ];
   }

}

#endif /* __CODEX_VSS_COMBINATORICSPLITTING_H__ */

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