1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
|
// 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)
/// \brief DL_GroupPrecomputation interface
/// \tparam T Field element
template <class T>
class DL_GroupPrecomputation
{
public:
typedef T Element;
virtual ~DL_GroupPrecomputation() {}
/// \brief Determines if elements needs conversion
/// \return true if the element needs conversion, false otherwise
/// \details NeedConversions determines if an element must convert between representations.
virtual bool NeedConversions() const {return false;}
/// \brief Converts an element between representations
/// \param v element to convert
/// \return an element converted to an alternate representation for internal use
/// \details ConvertIn is used when an element must convert between representations.
virtual Element ConvertIn(const Element &v) const {return v;}
/// \brief Converts an element between representations
/// \param v element to convert
/// \return an element converted from an alternate representation
virtual Element ConvertOut(const Element &v) const {return v;}
/// \brief Retrieves AbstractGroup interface
/// \return GetGroup() returns the AbstractGroup interface
virtual const AbstractGroup<Element> & GetGroup() const =0;
/// \brief Decodes element in DER format
/// \param bt BufferedTransformation object
/// \return element in the group
virtual Element BERDecodeElement(BufferedTransformation &bt) const =0;
/// \brief Encodes element in DER format
/// \param bt BufferedTransformation object
/// \param P Element to encode
virtual void DEREncodeElement(BufferedTransformation &bt, const Element &P) const =0;
};
/// \brief DL_FixedBasePrecomputation interface
/// \tparam T Field element
template <class T>
class DL_FixedBasePrecomputation
{
public:
typedef T Element;
virtual ~DL_FixedBasePrecomputation() {}
/// \brief Determines whether this object is initialized
/// \return true if this object is initialized, false otherwise
virtual bool IsInitialized() const =0;
/// \brief Set the base element
/// \param group the group
/// \param base element in the group
virtual void SetBase(const DL_GroupPrecomputation<Element> &group, const Element &base) =0;
/// \brief Get the base element
/// \param group the group
/// \return base element in the group
virtual const Element & GetBase(const DL_GroupPrecomputation<Element> &group) const =0;
/// \brief Perform precomputation
/// \param group the group
/// \param maxExpBits used to calculate the exponent base
/// \param storage the suggested number of objects for the precompute table
/// \details The exact semantics of Precompute() varies, but it typically means calculate
/// a table of n objects that can be used later to speed up computation.
/// \details If a derived class does not override Precompute(), then the base class throws
/// NotImplemented.
/// \sa SupportsPrecomputation(), LoadPrecomputation(), SavePrecomputation()
virtual void Precompute(const DL_GroupPrecomputation<Element> &group, unsigned int maxExpBits, unsigned int storage) =0;
/// \brief Retrieve previously saved precomputation
/// \param group the group
/// \param storedPrecomputation BufferedTransformation with the saved precomputation
/// \throw NotImplemented
/// \sa SupportsPrecomputation(), Precompute()
virtual void Load(const DL_GroupPrecomputation<Element> &group, BufferedTransformation &storedPrecomputation) =0;
/// \brief Save precomputation for later use
/// \param group the group
/// \param storedPrecomputation BufferedTransformation to write the precomputation
/// \throw NotImplemented
/// \sa SupportsPrecomputation(), Precompute()
virtual void Save(const DL_GroupPrecomputation<Element> &group, BufferedTransformation &storedPrecomputation) const =0;
/// \brief Exponentiates an element
/// \param group the group
/// \param exponent the exponent
/// \return the result of the exponentiation
virtual Element Exponentiate(const DL_GroupPrecomputation<Element> &group, const Integer &exponent) const =0;
/// \brief Exponentiates an element
/// \param pc1 the first the group precomputation
/// \param exponent1 the first exponent
/// \param pc2 the second the group precomputation
/// \param exponent2 the first exponent2
/// \return the public element raised to the exponent
/// \details CascadeExponentiateBaseAndPublicElement raises the public element to
/// the base element and precomputation.
virtual Element CascadeExponentiate(const DL_GroupPrecomputation<Element> &pc1, const Integer &exponent1, const DL_FixedBasePrecomputation<Element> &pc2, const Integer &exponent2) const =0;
};
/// \brief DL_FixedBasePrecomputation adapter class
/// \tparam T Field element
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> &pc1, const Integer &exponent1, 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
|
