1#ifndef CRYPTOPP_EC2N_H
2#define CRYPTOPP_EC2N_H
3
4#include "gf2n.h"
5#include "eprecomp.h"
6#include "smartptr.h"
7#include "pubkey.h"
8
9NAMESPACE_BEGIN(CryptoPP)
10
11//! Elliptic Curve Point
12struct CRYPTOPP_DLL EC2NPoint
13{
14	EC2NPoint() : identity(true) {}
15	EC2NPoint(const PolynomialMod2 &x, const PolynomialMod2 &y)
16		: identity(false), x(x), y(y) {}
17
18	bool operator==(const EC2NPoint &t) const
19		{return (identity && t.identity) || (!identity && !t.identity && x==t.x && y==t.y);}
20	bool operator< (const EC2NPoint &t) const
21		{return identity ? !t.identity : (!t.identity && (x<t.x || (x==t.x && y<t.y)));}
22
23	bool identity;
24	PolynomialMod2 x, y;
25};
26
27CRYPTOPP_DLL_TEMPLATE_CLASS AbstractGroup<EC2NPoint>;
28
29//! Elliptic Curve over GF(2^n)
30class CRYPTOPP_DLL EC2N : public AbstractGroup<EC2NPoint>
31{
32public:
33	typedef GF2NP Field;
34	typedef Field::Element FieldElement;
35	typedef EC2NPoint Point;
36
37	EC2N() {}
38	EC2N(const Field &field, const Field::Element &a, const Field::Element &b)
39		: m_field(field), m_a(a), m_b(b) {}
40	// construct from BER encoded parameters
41	// this constructor will decode and extract the the fields fieldID and curve of the sequence ECParameters
42	EC2N(BufferedTransformation &bt);
43
44	// encode the fields fieldID and curve of the sequence ECParameters
45	void DEREncode(BufferedTransformation &bt) const;
46
47	bool Equal(const Point &P, const Point &Q) const;
48	const Point& Identity() const;
49	const Point& Inverse(const Point &P) const;
50	bool InversionIsFast() const {return true;}
51	const Point& Add(const Point &P, const Point &Q) const;
52	const Point& Double(const Point &P) const;
53
54	Point Multiply(const Integer &k, const Point &P) const
55		{return ScalarMultiply(P, k);}
56	Point CascadeMultiply(const Integer &k1, const Point &P, const Integer &k2, const Point &Q) const
57		{return CascadeScalarMultiply(P, k1, Q, k2);}
58
59	bool ValidateParameters(RandomNumberGenerator &rng, unsigned int level=3) const;
60	bool VerifyPoint(const Point &P) const;
61
62	unsigned int EncodedPointSize(bool compressed = false) const
63		{return 1 + (compressed?1:2)*m_field->MaxElementByteLength();}
64	// returns false if point is compressed and not valid (doesn't check if uncompressed)
65	bool DecodePoint(Point &P, BufferedTransformation &bt, size_t len) const;
66	bool DecodePoint(Point &P, const byte *encodedPoint, size_t len) const;
67	void EncodePoint(byte *encodedPoint, const Point &P, bool compressed) const;
68	void EncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const;
69
70	Point BERDecodePoint(BufferedTransformation &bt) const;
71	void DEREncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const;
72
73	Integer FieldSize() const {return Integer::Power2(m_field->MaxElementBitLength());}
74	const Field & GetField() const {return *m_field;}
75	const FieldElement & GetA() const {return m_a;}
76	const FieldElement & GetB() const {return m_b;}
77
78	bool operator==(const EC2N &rhs) const
79		{return GetField() == rhs.GetField() && m_a == rhs.m_a && m_b == rhs.m_b;}
80
81private:
82	clonable_ptr<Field> m_field;
83	FieldElement m_a, m_b;
84	mutable Point m_R;
85};
86
87CRYPTOPP_DLL_TEMPLATE_CLASS DL_FixedBasePrecomputationImpl<EC2N::Point>;
88CRYPTOPP_DLL_TEMPLATE_CLASS DL_GroupPrecomputation<EC2N::Point>;
89
90template <class T> class EcPrecomputation;
91
92//! EC2N precomputation
93template<> class EcPrecomputation<EC2N> : public DL_GroupPrecomputation<EC2N::Point>
94{
95public:
96	typedef EC2N EllipticCurve;
97
98	// DL_GroupPrecomputation
99	const AbstractGroup<Element> & GetGroup() const {return m_ec;}
100	Element BERDecodeElement(BufferedTransformation &bt) const {return m_ec.BERDecodePoint(bt);}
101	void DEREncodeElement(BufferedTransformation &bt, const Element &v) const {m_ec.DEREncodePoint(bt, v, false);}
102
103	// non-inherited
104	void SetCurve(const EC2N &ec) {m_ec = ec;}
105	const EC2N & GetCurve() const {return m_ec;}
106
107private:
108	EC2N m_ec;
109};
110
111NAMESPACE_END
112
113#endif
114