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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
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