src/zerocoin/Accumulator.cpp

   1 /**
   2  * @file       Accumulator.cpp
   3  *
   4  * @brief      Accumulator and AccumulatorWitness classes for the Zerocoin library.
   5  *
   6  * @author     Ian Miers, Christina Garman and Matthew Green
   7  * @date       June 2013
   8  *
   9  * @copyright  Copyright 2013 Ian Miers, Christina Garman and Matthew Green
  10  * @license    This project is released under the MIT license.
  11  **/
  12
  13 #include <sstream>
  14 #include "Zerocoin.h"
  15
  16 namespace libzerocoin {
  17
  18 //Accumulator class
  19 Accumulator::Accumulator(const AccumulatorAndProofParams* p, const CoinDenomination d): params(p), denomination(d) {
  20         if (!(params->initialized)) {
  21                 throw ZerocoinException("Invalid parameters for accumulator");
  22         }
  23
  24         this->value = this->params->accumulatorBase;
  25 }
  26
  27 Accumulator::Accumulator(const Params* p, const CoinDenomination d) {
  28         this->params = &(p->accumulatorParams);
  29         this->denomination = d;
  30
  31         if (!(params->initialized)) {
  32                 throw ZerocoinException("Invalid parameters for accumulator");
  33         }
  34
  35         this->value = this->params->accumulatorBase;
  36 }
  37
  38 void Accumulator::accumulate(const PublicCoin& coin) {
  39         // Make sure we're initialized
  40         if(!(this->value)) {
  41                 throw ZerocoinException("Accumulator is not initialized");
  42         }
  43
  44         if(this->denomination != coin.getDenomination()) {
  45                 //std::stringstream msg;
  46                 std::string msg;
  47                 msg = "Wrong denomination for coin. Expected coins of denomination: ";
  48                 msg += this->denomination;
  49                 msg += ". Instead, got a coin of denomination: ";
  50                 msg += coin.getDenomination();
  51                 throw std::invalid_argument(msg);
  52         }
  53
  54         if(coin.validate()) {
  55                 // Compute new accumulator = "old accumulator"^{element} mod N
  56                 this->value = this->value.pow_mod(coin.getValue(), this->params->accumulatorModulus);
  57         } else {
  58                 throw std::invalid_argument("Coin is not valid");
  59         }
  60 }
  61
  62 const CoinDenomination Accumulator::getDenomination() const {
  63         return static_cast<CoinDenomination> (this->denomination);
  64 }
  65
  66 const Bignum& Accumulator::getValue() const {
  67         return this->value;
  68 }
  69
  70 Accumulator& Accumulator::operator += (const PublicCoin& c) {
  71         this->accumulate(c);
  72         return *this;
  73 }
  74
  75 bool Accumulator::operator == (const Accumulator rhs) const {
  76         return this->value == rhs.value;
  77 }
  78
  79 //AccumulatorWitness class
  80 AccumulatorWitness::AccumulatorWitness(const Params* p,
  81                                        const Accumulator& checkpoint, const PublicCoin coin): params(p), witness(checkpoint), element(coin) {
  82 }
  83
  84 void AccumulatorWitness::AddElement(const PublicCoin& c) {
  85         if(element != c) {
  86                 witness += c;
  87         }
  88 }
  89
  90 const Bignum& AccumulatorWitness::getValue() const {
  91         return this->witness.getValue();
  92 }
  93
  94 bool AccumulatorWitness::VerifyWitness(const Accumulator& a, const PublicCoin &publicCoin) const {
  95         Accumulator temp(witness);
  96         temp += element;
  97         return (temp == a && this->element == publicCoin);
  98 }
  99
 100 AccumulatorWitness& AccumulatorWitness::operator +=(
 101     const PublicCoin& rhs) {
 102         this->AddElement(rhs);
 103         return *this;
 104 }
 105
 106 } /* namespace libzerocoin */