// gf256.h - originally written and placed in the public domain by Wei Dai

/// \file gf256.h

/// \brief Classes and functions for schemes over GF(256)

#ifndef CRYPTOPP_GF256_H

#define CRYPTOPP_GF256_H

#include "cryptlib.h"

#include "misc.h"

NAMESPACE_BEGIN(CryptoPP)

/// \brief GF(256) with polynomial basis

class GF256

{

public:

  typedef byte Element;

  typedef int RandomizationParameter;

  GF256(byte modulus) : m_modulus(modulus) {}

  Element RandomElement(RandomNumberGenerator &rng, int ignored = 0) const

    {CRYPTOPP_UNUSED(ignored); return rng.GenerateByte();}

  bool Equal(Element a, Element b) const

    {return a==b;}

  Element Zero() const

    {return 0;}

  Element Add(Element a, Element b) const

    {return a^b;}

  Element& Accumulate(Element &a, Element b) const

    {return a^=b;}

  Element Inverse(Element a) const

    {return a;}

  Element Subtract(Element a, Element b) const

    {return a^b;}

  Element& Reduce(Element &a, Element b) const

    {return a^=b;}

  Element Double(Element a) const

    {CRYPTOPP_UNUSED(a); return 0;}

  Element One() const

    {return 1;}

  Element Multiply(Element a, Element b) const;

  Element Square(Element a) const

    {return Multiply(a, a);}

  bool IsUnit(Element a) const

    {return a != 0;}

  Element MultiplicativeInverse(Element a) const;

  Element Divide(Element a, Element b) const

    {return Multiply(a, MultiplicativeInverse(b));}

private:

  word m_modulus;

};

NAMESPACE_END

#endif