reducer.h

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/*
* Modular Reducer
* (C) 1999-2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
 
#ifndef BOTAN_MODULAR_REDUCER_H__
#define BOTAN_MODULAR_REDUCER_H__
 
#include <botan/numthry.h>
 
namespace Botan {
 
/**
* Modular Reducer (using Barrett's technique)
*/
class BOTAN_DLL Modular_Reducer
   {
   public:
      const BigInt& get_modulus() const { return modulus; }
 
      BigInt reduce(const BigInt& x) const;
 
      /**
      * Multiply mod p
      * @param x
      * @param y
      * @return (x * y) % p
      */
      BigInt multiply(const BigInt& x, const BigInt& y) const
         { return reduce(x * y); }
 
      /**
      * Square mod p
      * @param x
      * @return (x * x) % p
      */
      BigInt square(const BigInt& x) const
         { return reduce(Botan::square(x)); }
 
      /**
      * Cube mod p
      * @param x
      * @return (x * x * x) % p
      */
      BigInt cube(const BigInt& x) const
         { return multiply(x, this->square(x)); }
 
      bool initialized() const { return (mod_words != 0); }
 
      Modular_Reducer() { mod_words = 0; }
      Modular_Reducer(const BigInt& mod);
   private:
      BigInt modulus, modulus_2, mu;
      size_t mod_words;
   };
 
}
 
#endif