Crypto++  8.2
Free C++ class library of cryptographic schemes
ec2n.h
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1 // ec2n.h - originally written and placed in the public domain by Wei Dai
2 
3 /// \file ec2n.h
4 /// \brief Classes for Elliptic Curves over binary fields
5 
6 
7 #ifndef CRYPTOPP_EC2N_H
8 #define CRYPTOPP_EC2N_H
9 
10 #include "cryptlib.h"
11 #include "gf2n.h"
12 #include "integer.h"
13 #include "algebra.h"
14 #include "ecpoint.h"
15 #include "eprecomp.h"
16 #include "smartptr.h"
17 #include "pubkey.h"
18 
19 #if CRYPTOPP_MSC_VERSION
20 # pragma warning(push)
21 # pragma warning(disable: 4231 4275)
22 #endif
23 
24 NAMESPACE_BEGIN(CryptoPP)
25 
26 /// \brief Elliptic Curve over GF(2^n)
27 class CRYPTOPP_DLL EC2N : public AbstractGroup<EC2NPoint>, public EncodedPoint<EC2NPoint>
28 {
29 public:
30  typedef GF2NP Field;
31  typedef Field::Element FieldElement;
32  typedef EC2NPoint Point;
33 
34  virtual ~EC2N() {}
35 
36  /// \brief Construct an EC2N
37  EC2N() {}
38 
39  /// \brief Construct an EC2N
40  /// \param field Field, GF2NP derived class
41  /// \param a Field::Element
42  /// \param b Field::Element
43  EC2N(const Field &field, const Field::Element &a, const Field::Element &b)
44  : m_field(field), m_a(a), m_b(b) {}
45 
46  /// \brief Construct an EC2N from BER encoded parameters
47  /// \param bt BufferedTransformation derived object
48  /// \details This constructor will decode and extract the the fields fieldID and curve of the sequence ECParameters
50 
51  /// \brief Encode the fields fieldID and curve of the sequence ECParameters
52  /// \param bt BufferedTransformation derived object
53  void DEREncode(BufferedTransformation &bt) const;
54 
55  bool Equal(const Point &P, const Point &Q) const;
56  const Point& Identity() const;
57  const Point& Inverse(const Point &P) const;
58  bool InversionIsFast() const {return true;}
59  const Point& Add(const Point &P, const Point &Q) const;
60  const Point& Double(const Point &P) const;
61 
62  Point Multiply(const Integer &k, const Point &P) const
63  {return ScalarMultiply(P, k);}
64  Point CascadeMultiply(const Integer &k1, const Point &P, const Integer &k2, const Point &Q) const
65  {return CascadeScalarMultiply(P, k1, Q, k2);}
66 
67  bool ValidateParameters(RandomNumberGenerator &rng, unsigned int level=3) const;
68  bool VerifyPoint(const Point &P) const;
69 
70  unsigned int EncodedPointSize(bool compressed = false) const
71  {return 1 + (compressed?1:2)*m_field->MaxElementByteLength();}
72  // returns false if point is compressed and not valid (doesn't check if uncompressed)
73  bool DecodePoint(Point &P, BufferedTransformation &bt, size_t len) const;
74  bool DecodePoint(Point &P, const byte *encodedPoint, size_t len) const;
75  void EncodePoint(byte *encodedPoint, const Point &P, bool compressed) const;
76  void EncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const;
77 
78  Point BERDecodePoint(BufferedTransformation &bt) const;
79  void DEREncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const;
80 
81  Integer FieldSize() const {return Integer::Power2(m_field->MaxElementBitLength());}
82  const Field & GetField() const {return *m_field;}
83  const FieldElement & GetA() const {return m_a;}
84  const FieldElement & GetB() const {return m_b;}
85 
86  bool operator==(const EC2N &rhs) const
87  {return GetField() == rhs.GetField() && m_a == rhs.m_a && m_b == rhs.m_b;}
88 
89 private:
90  clonable_ptr<Field> m_field;
91  FieldElement m_a, m_b;
92  mutable Point m_R;
93 };
94 
95 CRYPTOPP_DLL_TEMPLATE_CLASS DL_FixedBasePrecomputationImpl<EC2N::Point>;
96 CRYPTOPP_DLL_TEMPLATE_CLASS DL_GroupPrecomputation<EC2N::Point>;
97 
98 /// \brief Elliptic Curve precomputation
99 /// \tparam EC elliptic curve field
100 template <class EC> class EcPrecomputation;
101 
102 /// \brief EC2N precomputation specialization
103 /// \details Implementation of <tt>DL_GroupPrecomputation<EC2N::Point></tt>
104 /// \sa DL_GroupPrecomputation
105 template<> class EcPrecomputation<EC2N> : public DL_GroupPrecomputation<EC2N::Point>
106 {
107 public:
108  typedef EC2N EllipticCurve;
109 
110  virtual ~EcPrecomputation() {}
111 
112  // DL_GroupPrecomputation
113  const AbstractGroup<Element> & GetGroup() const {return m_ec;}
114  Element BERDecodeElement(BufferedTransformation &bt) const {return m_ec.BERDecodePoint(bt);}
115  void DEREncodeElement(BufferedTransformation &bt, const Element &v) const {m_ec.DEREncodePoint(bt, v, false);}
116 
117  /// \brief Set the elliptic curve
118  /// \param ec ECP derived class
119  /// \details SetCurve() is not inherited
120  void SetCurve(const EC2N &ec) {m_ec = ec;}
121 
122  /// \brief Get the elliptic curve
123  /// \returns EC2N curve
124  /// \details GetCurve() is not inherited
125  const EC2N & GetCurve() const {return m_ec;}
126 
127 private:
128  EC2N m_ec;
129 };
130 
131 NAMESPACE_END
132 
133 #if CRYPTOPP_MSC_VERSION
134 # pragma warning(pop)
135 #endif
136 
137 #endif
Element BERDecodeElement(BufferedTransformation &bt) const
Decodes element in DER format.
Definition: ec2n.h:114
EC2N()
Construct an EC2N.
Definition: ec2n.h:37
This file contains helper classes/functions for implementing public key algorithms.
const AbstractGroup< Element > & GetGroup() const
Retrieves AbstractGroup interface.
Definition: ec2n.h:113
const char * Identity()
ConstByteArrayParameter.
Definition: argnames.h:94
unsigned int EncodedPointSize(bool compressed=false) const
Determines encoded point size.
Definition: ec2n.h:70
Abstract base classes that provide a uniform interface to this library.
Classes for automatic resource management.
Interface for random number generators.
Definition: cryptlib.h:1383
bool InversionIsFast() const
Determine if inversion is fast.
Definition: ec2n.h:58
Classes for Elliptic Curve points.
Classes for performing mathematics over different fields.
Interface for buffered transformations.
Definition: cryptlib.h:1598
bool operator==(const OID &lhs, const OID &rhs)
Compare two OIDs for equality.
void SetCurve(const EC2N &ec)
Set the elliptic curve.
Definition: ec2n.h:120
EC2N(const Field &field, const Field::Element &a, const Field::Element &b)
Construct an EC2N.
Definition: ec2n.h:43
A pointer which can be copied and cloned.
Definition: smartptr.h:103
static Integer CRYPTOPP_API Power2(size_t e)
Exponentiates to a power of 2.
Definition: integer.cpp:3079
Multiple precision integer with arithmetic operations.
Definition: integer.h:49
Elliptic Curve over GF(2^n)
Definition: ec2n.h:27
Classes and functions for schemes over GF(2^n)
Abstract group.
Definition: algebra.h:26
Classes for precomputation in a group.
GF(2^n) with Polynomial Basis.
Definition: gf2n.h:296
Abstract class for encoding and decoding ellicptic curve points.
Definition: ecpoint.h:90
Elliptic Curve precomputation.
Definition: ec2n.h:100
Multiple precision integer with arithmetic operations.
const EC2N & GetCurve() const
Get the elliptic curve.
Definition: ec2n.h:125
Crypto++ library namespace.
Elliptical Curve Point over GF(2^n)
Definition: ecpoint.h:53
DL_FixedBasePrecomputation adapter class.
Definition: eprecomp.h:126
void DEREncodeElement(BufferedTransformation &bt, const Element &v) const
Encodes element in DER format.
Definition: ec2n.h:115