def_powm.h

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/*
* Modular Exponentiation
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
 
#ifndef BOTAN_DEFAULT_MODEXP_H__
#define BOTAN_DEFAULT_MODEXP_H__
 
#include <botan/pow_mod.h>
#include <botan/reducer.h>
#include <vector>
 
namespace Botan {
 
/**
* Fixed Window Exponentiator
*/
class Fixed_Window_Exponentiator : public Modular_Exponentiator
   {
   public:
      void set_exponent(const BigInt&);
      void set_base(const BigInt&);
      BigInt execute() const;
 
      Modular_Exponentiator* copy() const
         { return new Fixed_Window_Exponentiator(*this); }
 
      Fixed_Window_Exponentiator(const BigInt&, Power_Mod::Usage_Hints);
   private:
      Modular_Reducer reducer;
      BigInt exp;
      size_t window_bits;
      std::vector<BigInt> g;
      Power_Mod::Usage_Hints hints;
   };
 
/**
* Montgomery Exponentiator
*/
class Montgomery_Exponentiator : public Modular_Exponentiator
   {
   public:
      void set_exponent(const BigInt&);
      void set_base(const BigInt&);
      BigInt execute() const;
 
      Modular_Exponentiator* copy() const
         { return new Montgomery_Exponentiator(*this); }
 
      Montgomery_Exponentiator(const BigInt&, Power_Mod::Usage_Hints);
   private:
      BigInt exp, modulus;
      BigInt R2, R_mod;
      std::vector<BigInt> g;
      word mod_prime;
      size_t mod_words, exp_bits, window_bits;
      Power_Mod::Usage_Hints hints;
   };
 
}
 
#endif