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/*
* Modular Reducer
* (C) 1999-2010 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#ifndef BOTAN_MODULAR_REDUCER_H_
#define BOTAN_MODULAR_REDUCER_H_
#include <botan/numthry.h>
namespace Botan {
/**
* Modular Reducer (using Barrett's technique)
*/
class BOTAN_PUBLIC_API(2,0) Modular_Reducer
{
public:
const BigInt& get_modulus() const { return m_modulus; }
BigInt reduce(const BigInt& x) const;
/**
* Multiply mod p
* @param x the first operand
* @param y the second operand
* @return (x * y) % p
*/
BigInt multiply(const BigInt& x, const BigInt& y) const
{ return reduce(x * y); }
/**
* Square mod p
* @param x the value to square
* @return (x * x) % p
*/
BigInt square(const BigInt& x) const
{ return reduce(Botan::square(x)); }
/**
* Cube mod p
* @param x the value to cube
* @return (x * x * x) % p
*/
BigInt cube(const BigInt& x) const
{ return multiply(x, this->square(x)); }
/**
* Low level reduction function. Mostly for internal use.
* Sometimes useful for performance by reducing temporaries
* Reduce x mod p and place the output in out. ** X and out must not reference each other **
* ws is a temporary workspace.
*/
void reduce(BigInt& out, const BigInt& x, secure_vector<word>& ws) const;
bool initialized() const { return (m_mod_words != 0); }
Modular_Reducer() { m_mod_words = 0; }
explicit Modular_Reducer(const BigInt& mod);
private:
BigInt m_modulus, m_mu;
size_t m_mod_words;
};
}
#endif
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