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

#include "pch.h"

#include "gf256.h"

NAMESPACE_BEGIN(CryptoPP)

GF256::Element GF256::Multiply(Element a, Element b) const

{

  word result = 0, t = b;

  for (unsigned int i=0; i<8; i++)

  {

    result <<= 1;

    if (result & 0x100)

      result ^= m_modulus;

    t <<= 1;

    if (t & 0x100)

      result ^= a;

  }

  return (GF256::Element) result;

}

GF256::Element GF256::MultiplicativeInverse(Element a) const

{

  Element result = a;

  for (int i=1; i<7; i++)

    result = Multiply(Square(result), a);

  return Square(result);

}

NAMESPACE_END