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// eprecomp.h - originally written and placed in the public domain by Wei Dai
//! \file eprecomp.h
//! \brief Classes for precomputation in a group
#ifndef CRYPTOPP_EPRECOMP_H
#define CRYPTOPP_EPRECOMP_H
#include "cryptlib.h"
#include "integer.h"
#include "algebra.h"
#include "stdcpp.h"
NAMESPACE_BEGIN(CryptoPP)
template <class T>
class DL_GroupPrecomputation
{
public:
typedef T Element;
virtual ~DL_GroupPrecomputation() {}
virtual bool NeedConversions() const {return false;}
virtual Element ConvertIn(const Element &v) const {return v;}
virtual Element ConvertOut(const Element &v) const {return v;}
virtual const AbstractGroup<Element> & GetGroup() const =0;
virtual Element BERDecodeElement(BufferedTransformation &bt) const =0;
virtual void DEREncodeElement(BufferedTransformation &bt, const Element &P) const =0;
};
template <class T>
class DL_FixedBasePrecomputation
{
public:
typedef T Element;
virtual ~DL_FixedBasePrecomputation() {}
virtual bool IsInitialized() const =0;
virtual void SetBase(const DL_GroupPrecomputation<Element> &group, const Element &base) =0;
virtual const Element & GetBase(const DL_GroupPrecomputation<Element> &group) const =0;
virtual void Precompute(const DL_GroupPrecomputation<Element> &group, unsigned int maxExpBits, unsigned int storage) =0;
virtual void Load(const DL_GroupPrecomputation<Element> &group, BufferedTransformation &storedPrecomputation) =0;
virtual void Save(const DL_GroupPrecomputation<Element> &group, BufferedTransformation &storedPrecomputation) const =0;
virtual Element Exponentiate(const DL_GroupPrecomputation<Element> &group, const Integer &exponent) const =0;
virtual Element CascadeExponentiate(const DL_GroupPrecomputation<Element> &group, const Integer &exponent, const DL_FixedBasePrecomputation<Element> &pc2, const Integer &exponent2) const =0;
};
template <class T>
class DL_FixedBasePrecomputationImpl : public DL_FixedBasePrecomputation<T>
{
public:
typedef T Element;
virtual ~DL_FixedBasePrecomputationImpl() {}
DL_FixedBasePrecomputationImpl() : m_windowSize(0) {}
// DL_FixedBasePrecomputation
bool IsInitialized() const
{return !m_bases.empty();}
void SetBase(const DL_GroupPrecomputation<Element> &group, const Element &base);
const Element & GetBase(const DL_GroupPrecomputation<Element> &group) const
{return group.NeedConversions() ? m_base : m_bases[0];}
void Precompute(const DL_GroupPrecomputation<Element> &group, unsigned int maxExpBits, unsigned int storage);
void Load(const DL_GroupPrecomputation<Element> &group, BufferedTransformation &storedPrecomputation);
void Save(const DL_GroupPrecomputation<Element> &group, BufferedTransformation &storedPrecomputation) const;
Element Exponentiate(const DL_GroupPrecomputation<Element> &group, const Integer &exponent) const;
Element CascadeExponentiate(const DL_GroupPrecomputation<Element> &group, const Integer &exponent, const DL_FixedBasePrecomputation<Element> &pc2, const Integer &exponent2) const;
private:
void PrepareCascade(const DL_GroupPrecomputation<Element> &group, std::vector<BaseAndExponent<Element> > &eb, const Integer &exponent) const;
Element m_base;
unsigned int m_windowSize;
Integer m_exponentBase; // what base to represent the exponent in
std::vector<Element> m_bases; // precalculated bases
};
NAMESPACE_END
#ifdef CRYPTOPP_MANUALLY_INSTANTIATE_TEMPLATES
#include "eprecomp.cpp"
#endif
#endif
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