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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 "ecpoint.h"
#include "eprecomp.h"
#include "smartptr.h"
#include "pubkey.h"
NAMESPACE_BEGIN(CryptoPP)
//! \class EC2N
//! \brief Elliptic Curve over GF(2^n)
class CRYPTOPP_DLL EC2N : public AbstractGroup<EC2NPoint>, public EncodedPoint<EC2NPoint>
{
public:
typedef GF2NP Field;
typedef Field::Element FieldElement;
typedef EC2NPoint Point;
virtual ~EC2N() {}
//! \brief Construct an EC2N
EC2N() {}
//! \brief Construct an EC2N
//! \param field Field, GF2NP derived class
//! \param a Field::Element
//! \param b Field::Element
EC2N(const Field &field, const Field::Element &a, const Field::Element &b)
: m_field(field), m_a(a), m_b(b) {}
//! \brief Construct an EC2N from BER encoded parameters
//! \param bt BufferedTransformation derived object
//! \details This constructor will decode and extract the the fields fieldID and curve of the sequence ECParameters
EC2N(BufferedTransformation &bt);
//! \brief Encode the fields fieldID and curve of the sequence ECParameters
//! \param bt BufferedTransformation derived object
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>;
//! \class EcPrecomputation
//! \brief Elliptic Curve precomputation
//! \tparam EC elliptic curve field
template <class EC> class EcPrecomputation;
//! \class EcPrecomputation<EC2N>
//! \brief EC2N precomputation specialization
//! \details Implementation of <tt>DL_GroupPrecomputation<EC2N::Point></tt>
//! \sa DL_GroupPrecomputation
template<> class EcPrecomputation<EC2N> : public DL_GroupPrecomputation<EC2N::Point>
{
public:
typedef EC2N EllipticCurve;
virtual ~EcPrecomputation() {}
// 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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