gf256.h

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// 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