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// ec2n.h - written and placed in the public domain by Wei Dai
//! \file
//! \headerfile ec2n.h
//! \brief Classes for Elliptic Curves over binary fields
#ifndef CRYPTOPP_EC2N_H
#define CRYPTOPP_EC2N_H
#include "cryptlib.h"
#include "gf2n.h"
#include "integer.h"
#include "algebra.h"
#include "eprecomp.h"
#include "smartptr.h"
#include "pubkey.h"
NAMESPACE_BEGIN(CryptoPP)
//! Elliptic Curve Point
struct CRYPTOPP_DLL EC2NPoint
{
#ifndef CRYPTOPP_MAINTAIN_BACKWARDS_COMPATIBILITY_562
virtual ~EC2NPoint() {}
#endif
EC2NPoint() : identity(true) {}
EC2NPoint(const PolynomialMod2 &x, const PolynomialMod2 &y)
: x(x), y(y), identity(false) {}
bool operator==(const EC2NPoint &t) const
{return (identity && t.identity) || (!identity && !t.identity && x==t.x && y==t.y);}
bool operator< (const EC2NPoint &t) const
{return identity ? !t.identity : (!t.identity && (x<t.x || (x==t.x && y<t.y)));}
PolynomialMod2 x, y;
bool identity;
};
CRYPTOPP_DLL_TEMPLATE_CLASS AbstractGroup<EC2NPoint>;
//! Elliptic Curve over GF(2^n)
class CRYPTOPP_DLL EC2N : public AbstractGroup<EC2NPoint>
{
public:
typedef GF2NP Field;
typedef Field::Element FieldElement;
typedef EC2NPoint Point;
#ifndef CRYPTOPP_MAINTAIN_BACKWARDS_COMPATIBILITY_562
virtual ~EC2N() {}
#endif
EC2N() {}
EC2N(const Field &field, const Field::Element &a, const Field::Element &b)
: m_field(field), m_a(a), m_b(b) {}
// construct from BER encoded parameters
// this constructor will decode and extract the the fields fieldID and curve of the sequence ECParameters
EC2N(BufferedTransformation &bt);
// encode the fields fieldID and curve of the sequence ECParameters
void DEREncode(BufferedTransformation &bt) const;
bool Equal(const Point &P, const Point &Q) const;
const Point& Identity() const;
const Point& Inverse(const Point &P) const;
bool InversionIsFast() const {return true;}
const Point& Add(const Point &P, const Point &Q) const;
const Point& Double(const Point &P) const;
Point Multiply(const Integer &k, const Point &P) const
{return ScalarMultiply(P, k);}
Point CascadeMultiply(const Integer &k1, const Point &P, const Integer &k2, const Point &Q) const
{return CascadeScalarMultiply(P, k1, Q, k2);}
bool ValidateParameters(RandomNumberGenerator &rng, unsigned int level=3) const;
bool VerifyPoint(const Point &P) const;
unsigned int EncodedPointSize(bool compressed = false) const
{return 1 + (compressed?1:2)*m_field->MaxElementByteLength();}
// returns false if point is compressed and not valid (doesn't check if uncompressed)
bool DecodePoint(Point &P, BufferedTransformation &bt, size_t len) const;
bool DecodePoint(Point &P, const byte *encodedPoint, size_t len) const;
void EncodePoint(byte *encodedPoint, const Point &P, bool compressed) const;
void EncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const;
Point BERDecodePoint(BufferedTransformation &bt) const;
void DEREncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const;
Integer FieldSize() const {return Integer::Power2(m_field->MaxElementBitLength());}
const Field & GetField() const {return *m_field;}
const FieldElement & GetA() const {return m_a;}
const FieldElement & GetB() const {return m_b;}
bool operator==(const EC2N &rhs) const
{return GetField() == rhs.GetField() && m_a == rhs.m_a && m_b == rhs.m_b;}
private:
clonable_ptr<Field> m_field;
FieldElement m_a, m_b;
mutable Point m_R;
};
CRYPTOPP_DLL_TEMPLATE_CLASS DL_FixedBasePrecomputationImpl<EC2N::Point>;
CRYPTOPP_DLL_TEMPLATE_CLASS DL_GroupPrecomputation<EC2N::Point>;
template <class T> class EcPrecomputation;
//! EC2N precomputation
template<> class EcPrecomputation<EC2N> : public DL_GroupPrecomputation<EC2N::Point>
{
public:
typedef EC2N EllipticCurve;
#ifndef CRYPTOPP_MAINTAIN_BACKWARDS_COMPATIBILITY_562
virtual ~EcPrecomputation() {}
#endif
// DL_GroupPrecomputation
const AbstractGroup<Element> & GetGroup() const {return m_ec;}
Element BERDecodeElement(BufferedTransformation &bt) const {return m_ec.BERDecodePoint(bt);}
void DEREncodeElement(BufferedTransformation &bt, const Element &v) const {m_ec.DEREncodePoint(bt, v, false);}
// non-inherited
void SetCurve(const EC2N &ec) {m_ec = ec;}
const EC2N & GetCurve() const {return m_ec;}
private:
EC2N m_ec;
};
NAMESPACE_END
#endif
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