You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
113 lines
3.7 KiB
113 lines
3.7 KiB
// eprecomp.cpp - written and placed in the public domain by Wei Dai
|
|
|
|
#include "pch.h"
|
|
|
|
#ifndef CRYPTOPP_IMPORTS
|
|
|
|
#include "eprecomp.h"
|
|
#include "integer.h"
|
|
#include "asn.h"
|
|
|
|
NAMESPACE_BEGIN(CryptoPP)
|
|
|
|
template <class T> void DL_FixedBasePrecomputationImpl<T>::SetBase(const DL_GroupPrecomputation<Element> &group, const Element &i_base)
|
|
{
|
|
m_base = group.NeedConversions() ? group.ConvertIn(i_base) : i_base;
|
|
|
|
if (m_bases.empty() || !(m_base == m_bases[0]))
|
|
{
|
|
m_bases.resize(1);
|
|
m_bases[0] = m_base;
|
|
}
|
|
|
|
if (group.NeedConversions())
|
|
m_base = i_base;
|
|
}
|
|
|
|
template <class T> void DL_FixedBasePrecomputationImpl<T>::Precompute(const DL_GroupPrecomputation<Element> &group, unsigned int maxExpBits, unsigned int storage)
|
|
{
|
|
assert(m_bases.size() > 0);
|
|
assert(storage <= maxExpBits);
|
|
|
|
if (storage > 1)
|
|
{
|
|
m_windowSize = (maxExpBits+storage-1)/storage;
|
|
m_exponentBase = Integer::Power2(m_windowSize);
|
|
}
|
|
|
|
m_bases.resize(storage);
|
|
for (unsigned i=1; i<storage; i++)
|
|
m_bases[i] = group.GetGroup().ScalarMultiply(m_bases[i-1], m_exponentBase);
|
|
}
|
|
|
|
template <class T> void DL_FixedBasePrecomputationImpl<T>::Load(const DL_GroupPrecomputation<Element> &group, BufferedTransformation &bt)
|
|
{
|
|
BERSequenceDecoder seq(bt);
|
|
word32 version;
|
|
BERDecodeUnsigned<word32>(seq, version, INTEGER, 1, 1);
|
|
m_exponentBase.BERDecode(seq);
|
|
m_windowSize = m_exponentBase.BitCount() - 1;
|
|
m_bases.clear();
|
|
while (!seq.EndReached())
|
|
m_bases.push_back(group.BERDecodeElement(seq));
|
|
if (!m_bases.empty() && group.NeedConversions())
|
|
m_base = group.ConvertOut(m_bases[0]);
|
|
seq.MessageEnd();
|
|
}
|
|
|
|
template <class T> void DL_FixedBasePrecomputationImpl<T>::Save(const DL_GroupPrecomputation<Element> &group, BufferedTransformation &bt) const
|
|
{
|
|
DERSequenceEncoder seq(bt);
|
|
DEREncodeUnsigned<word32>(seq, 1); // version
|
|
m_exponentBase.DEREncode(seq);
|
|
for (unsigned i=0; i<m_bases.size(); i++)
|
|
group.DEREncodeElement(seq, m_bases[i]);
|
|
seq.MessageEnd();
|
|
}
|
|
|
|
template <class T> void DL_FixedBasePrecomputationImpl<T>::PrepareCascade(const DL_GroupPrecomputation<Element> &i_group, std::vector<BaseAndExponent<Element> > &eb, const Integer &exponent) const
|
|
{
|
|
const AbstractGroup<T> &group = i_group.GetGroup();
|
|
|
|
Integer r, q, e = exponent;
|
|
bool fastNegate = group.InversionIsFast() && m_windowSize > 1;
|
|
unsigned int i;
|
|
|
|
for (i=0; i+1<m_bases.size(); i++)
|
|
{
|
|
Integer::DivideByPowerOf2(r, q, e, m_windowSize);
|
|
std::swap(q, e);
|
|
if (fastNegate && r.GetBit(m_windowSize-1))
|
|
{
|
|
++e;
|
|
eb.push_back(BaseAndExponent<Element>(group.Inverse(m_bases[i]), m_exponentBase - r));
|
|
}
|
|
else
|
|
eb.push_back(BaseAndExponent<Element>(m_bases[i], r));
|
|
}
|
|
eb.push_back(BaseAndExponent<Element>(m_bases[i], e));
|
|
}
|
|
|
|
template <class T> T DL_FixedBasePrecomputationImpl<T>::Exponentiate(const DL_GroupPrecomputation<Element> &group, const Integer &exponent) const
|
|
{
|
|
std::vector<BaseAndExponent<Element> > eb; // array of segments of the exponent and precalculated bases
|
|
eb.reserve(m_bases.size());
|
|
PrepareCascade(group, eb, exponent);
|
|
return group.ConvertOut(GeneralCascadeMultiplication<Element>(group.GetGroup(), eb.begin(), eb.end()));
|
|
}
|
|
|
|
template <class T> T
|
|
DL_FixedBasePrecomputationImpl<T>::CascadeExponentiate(const DL_GroupPrecomputation<Element> &group, const Integer &exponent,
|
|
const DL_FixedBasePrecomputation<T> &i_pc2, const Integer &exponent2) const
|
|
{
|
|
std::vector<BaseAndExponent<Element> > eb; // array of segments of the exponent and precalculated bases
|
|
const DL_FixedBasePrecomputationImpl<T> &pc2 = static_cast<const DL_FixedBasePrecomputationImpl<T> &>(i_pc2);
|
|
eb.reserve(m_bases.size() + pc2.m_bases.size());
|
|
PrepareCascade(group, eb, exponent);
|
|
pc2.PrepareCascade(group, eb, exponent2);
|
|
return group.ConvertOut(GeneralCascadeMultiplication<Element>(group.GetGroup(), eb.begin(), eb.end()));
|
|
}
|
|
|
|
NAMESPACE_END
|
|
|
|
#endif
|