wiselib.testing/algorithms/crypto/ZeroKnowledgeProofsFp/schnorr-zkp-verifier.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.      **
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 ** License, or (at your option) any later version.                       **
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 ** 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.                                       **
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#ifndef __ALGORITHMS_SCHNORRZKP_VERIFIER_H_
#define __ALGORITHMS_SCHNORRZKP_VERIFIER_H_

#include "algorithms/crypto/eccfp.h"
#include "algorithms/crypto/sha1.h"

#include <string.h>

//protocol needs to be executed for 1 round
#define REQ_ROUNDS 1

// Uncomment to enable Debug
#define ENABLE_SCHNORRZKP_DEBUG

/* PROTOCOL DESCRIPTION

Schnorr's Protocol

Prover and Verifier agree on an elliptic curve E over a field Fn , a generator
G in E/Fn . They both know B in E/Fn and Prover claims he knows x such
that B = x * G.

Protocol Steps

1. Prover generates random r and computes A = r * G
2. Prover sends A to Verifier
3. Verifier computes c = HASH(G, B, A) and sends c to Prover
4. Prover computes m = r + cx and sends m to Verifier
5 Verifier checks that P = m*G-c*B =(r+cx)*G-c*B = r*G+cx*G - c*xG = A
and that HASH(G, B, P ) = c.
*/

namespace wiselib {

template<typename OsModel_P, typename Radio_P = typename OsModel_P::Radio, typename Debug_P = typename OsModel_P::Debug>
   class SCHNORRZKPVerify
   {
   public:
      typedef OsModel_P OsModel;
      typedef Radio_P Radio;
      typedef Debug_P Debug;

      typedef SCHNORRZKPVerify<OsModel_P, Radio_P, Debug_P> self_t;
     typedef typename Radio::node_id_t node_id_t;
     typedef typename Radio::size_t size_t;
     typedef typename Radio::block_data_t block_data_t;
     typedef self_t* self_pointer_t;

      SCHNORRZKPVerify();
      ~SCHNORRZKPVerify();


      //message types
      //message types
      enum MsgHeaders {
        START_MSG = 200,
        HASH_MSG = 201,
        CONT_MSG = 202,
        ACCEPT_MSG = 203,
        REJECT_MSG = 204
       };

      int init( Radio& radio, Debug& debug )
     {
       radio_ = &radio;
       debug_ = &debug;
       return 0;
     }

      inline int init();
     inline int destruct();

     int enable_radio( void );
     int disable_radio( void );

      void key_setup(Point *pubkey);
      void compute_hash();
      void verify();
      void final_decision();

   protected:
           void receive( node_id_t from, size_t len, block_data_t *data );

   private:

   Radio& radio()
   { return *radio_; }

   Debug& debug()
   { return *debug_; }

   typename Radio::self_pointer_t radio_;
   typename Debug::self_pointer_t debug_;

   //necessary class objects
   ECCFP eccfp;
   PMP pmp;

      //# of successfull rounds
   uint8_t success_rounds;

   //# of required rounds
   uint8_t required_rounds;

   //the hash calculated on the point received by the prover
   NN_DIGIT c[NUMWORDS];

   //private key that will be received by the prover in each round
   NN_DIGIT Valid[NUMWORDS];

   //public key that both prover and verifier know
   Point B;

   //public key A to be received by the prover
   Point A;

   //public key P for the verifications
   Point P;

   };

   // -----------------------------------------------------------------------
   template<typename OsModel_P,
         typename Radio_P,
         typename Debug_P>
   SCHNORRZKPVerify<OsModel_P, Radio_P, Debug_P>::
	SCHNORRZKPVerify()
   :radio_(0),
    debug_(0)
   {}

   // -----------------------------------------------------------------------
   template<typename OsModel_P,
         typename Radio_P,
         typename Debug_P>
   SCHNORRZKPVerify<OsModel_P, Radio_P, Debug_P>::
	~SCHNORRZKPVerify()
   {}

   //-----------------------------------------------------------------------
   template<typename OsModel_P,
         typename Radio_P,
         typename Debug_P>
   int
   SCHNORRZKPVerify<OsModel_P, Radio_P, Debug_P>::
	init( void )
   {
     enable_radio();
     return 0;
   }
   //-----------------------------------------------------------------------------
   template<typename OsModel_P,
         typename Radio_P,
         typename Debug_P>
   int
   SCHNORRZKPVerify<OsModel_P, Radio_P, Debug_P>::
	destruct( void )
   {
     return disable_radio();
   }
   //---------------------------------------------------------------------------
   template<typename OsModel_P,
         typename Radio_P,
         typename Debug_P>
   int
   SCHNORRZKPVerify<OsModel_P, Radio_P, Debug_P>::
	enable_radio( void )
   {
#ifdef ENABLE_SCHNORRZKP_DEBUG
      debug().debug( "SCHNORR-ZKP-Verify: Boot for %i\n", radio().id() );
#endif

     radio().enable_radio();
     radio().template reg_recv_callback<self_t, &self_t::receive>( this );

     return 0;
   }
   //---------------------------------------------------------------------------
   template<typename OsModel_P,
         typename Radio_P,
         typename Debug_P>
   int
   SCHNORRZKPVerify<OsModel_P, Radio_P, Debug_P>::
	disable_radio( void )
   {
#ifdef ENABLE_SCHNORRZKP_DEBUG
      debug().debug( "SCHNORR-ZKP-Verify: Disable\n" );
#endif
     return -1;
   }
   //----------------------------------------------------------------------
   template<typename OsModel_P,
            typename Radio_P,
            typename Debug_P>
   void
   SCHNORRZKPVerify<OsModel_P, Radio_P, Debug_P>::
	key_setup( Point *pubkey ) {

#ifdef ENABLE_SCHNORRZKP_DEBUG
      debug().debug("Debug::Start Schnorr Interactive ZKP Verifier on::%d \n", radio().id() );
#endif
      success_rounds=0;
      required_rounds = REQ_ROUNDS;

      //copy keys to local variables
      //public key available to prover and verifier
      eccfp.p_clear(&B);
      eccfp.p_copy(&B, pubkey);
   }

   //------------------------------------------------------------------------------------
   template<typename OsModel_P,
               typename Radio_P,
               typename Debug_P>
   void
   SCHNORRZKPVerify<OsModel_P, Radio_P, Debug_P>::
	compute_hash(){
#ifdef ENABLE_SCHNORRZKP_DEBUG
      debug().debug("Debug::Starting computing the hash on the point received by prover!\n", radio().id() );
#endif

      //task for the verifier to compute the hash c
      //c = HASH( G, B, A)
      block_data_t input[6*(KEYDIGITS*NN_DIGIT_LEN + 1)];
      block_data_t b[20];
      //convert point G to octet and place to input
      eccfp.point2octet(input, 2*(KEYDIGITS*NN_DIGIT_LEN + 1), &param.G, FALSE);
      //convert point B to octet and place to input
      eccfp.point2octet(input + 2*(KEYDIGITS*NN_DIGIT_LEN + 1), 2*(KEYDIGITS*NN_DIGIT_LEN + 1), &B, FALSE);
      //convert point A to octet and place to input
      eccfp.point2octet(input + 4*(KEYDIGITS*NN_DIGIT_LEN + 1), 2*(KEYDIGITS*NN_DIGIT_LEN + 1), &A, FALSE);

      //digest
      SHA1Context sha;
      SHA1::SHA1Reset(&sha);
      SHA1::SHA1Update(&sha, input, 6*(KEYDIGITS*NN_DIGIT_LEN + 1));
      SHA1::SHA1Digest(&sha, b);

      //place the hash on a private key
      NN_DIGIT key[NUMWORDS];
      pmp.AssignZero(key, NUMWORDS);
      //decode the private key received
      pmp.Decode(key, NUMWORDS, b, 20);

      //mod n the hash output
      pmp.Mod(c, key, NUMWORDS, param.r, NUMWORDS);

      //convert c to octet, place c to buffer
      //and send the hash c to the prover
      block_data_t buffer[KEYDIGITS * NN_DIGIT_LEN +2];
      buffer[0]=HASH_MSG;
      pmp.Encode(buffer+1, KEYDIGITS * NN_DIGIT_LEN +1, c, NUMWORDS);

#ifdef ENABLE_SCHNORRZKP_DEBUG
      debug().debug("Debug::Finished hash calculation!Sending the hash to prover. ::%d \n", radio().id() );
#endif
      radio().send(Radio::BROADCAST_ADDRESS, KEYDIGITS * NN_DIGIT_LEN +2 , buffer);
   }

   //------------------------------------------------------------------------------------
   template<typename OsModel_P,
            typename Radio_P,
            typename Debug_P>
   void
   SCHNORRZKPVerify<OsModel_P, Radio_P, Debug_P>::
	verify(){
#ifdef ENABLE_SCHNORRZKP_DEBUG
      debug().debug("Debug::Starting Verify!\n", radio().id() );
#endif
      //verifier checks that A + cB = xG
      Point result;
      Point result1;
      eccfp.p_clear(&result);
      eccfp.p_clear(&result1);
      eccfp.p_clear(&P);

      //compute xG
      eccfp.gen_public_key(&result, Valid);

      //compute cB
      eccfp.c_mul(&result1, &B, c);

      //compute A + cB
      eccfp.c_add_affine(&P, &result1, &A);

      //is the result correct???
      //compare point A with point P
      if(eccfp.p_equal(&result,&P)==true)
      {
         success_rounds++;
#ifdef ENABLE_SCHNORRZKP_DEBUG
         debug().debug("Debug::Check SUCCESS!\n", radio().id() );
#endif
      }
      else
      {
#ifdef ENABLE_SCHNORRZKP_DEBUG
         debug().debug( "Debug::Check FAIL!\n", radio().id() );
#endif
      }

      //call the task final decision
      final_decision();
   }

   //----------------------------------------------------------------------------------------
   template<typename OsModel_P,
            typename Radio_P,
            typename Debug_P>
   void
   SCHNORRZKPVerify<OsModel_P, Radio_P, Debug_P>::
	final_decision(){

      //were the round successful??the protocol accepts
      if(success_rounds==required_rounds)
      {
#ifdef ENABLE_SCHNORRZKP_DEBUG
         debug().debug("Debug::Protocol finished with success.Secret Verified!!Prover HONEST!\n", radio().id() );
#endif
         //send to prover the accept message
         block_data_t buffer[1];
         buffer[0]=ACCEPT_MSG;
         radio().send(Radio::BROADCAST_ADDRESS, 1, buffer);
      }
      //the round failed, the protocol rejects
      else
      {
#ifdef ENABLE_SCHNORRZKP_DEBUG
         debug().debug("Debug::Protocol finished without success.Secret NOT Verified!!Prover NOT HONEST\n", radio().id() );
#endif
         block_data_t buffer[1];
         buffer[0]=REJECT_MSG;
         radio().send(Radio::BROADCAST_ADDRESS, 1, buffer);
      }
   }

   //---------------------------------------------------------------------------
   template<typename OsModel_P,
            typename Radio_P,
            typename Debug_P>
   void
   SCHNORRZKPVerify<OsModel_P, Radio_P, Debug_P>::
	receive( node_id_t from, size_t len, block_data_t *data ) {

      if( from == radio().id() ) return;

      if(data[0]==START_MSG)
      {
#ifdef ENABLE_SCHNORRZKP_DEBUG
         debug().debug("Debug::Received a starting message::%d \n", radio().id() );
#endif

         //get Verify point A from the message
         eccfp.p_clear(&A);

         //convert octet received to point A
         eccfp.octet2point(&A, data+1, 2*(KEYDIGITS * NN_DIGIT_LEN +1));

         //call the task to compute hash
         compute_hash();
      }

      if(data[0]==CONT_MSG)
      {
#ifdef ENABLE_SCHNORRZKP_DEBUG
         debug().debug("Debug::Received a continue message::%d \n", radio().id() );
#endif

         //get private key x and place to Valid
         pmp.AssignZero(Valid, NUMWORDS);
         //decode the private key received
         pmp.Decode(Valid, NUMWORDS, data+1, KEYDIGITS * NN_DIGIT_LEN +1);

         //call the task for verification
         verify();
      }

   }

} //end of wiselib namespace

#endif /* SCNORRZKP_VERIFIER_H_ */