// ec2n.h - originally written and placed in the public domain by Wei Dai

/// \file 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"

#if CRYPTOPP_MSC_VERSION

# pragma warning(push)

# pragma warning(disable: 4231 4275)

#endif

NAMESPACE_BEGIN(CryptoPP)

/// \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 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>;

/// \brief Elliptic Curve precomputation

/// \tparam EC elliptic curve field

template <class EC> class EcPrecomputation;

/// \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);}

  /// \brief Set the elliptic curve

  /// \param ec ECP derived class

  /// \details SetCurve() is not inherited

  void SetCurve(const EC2N &ec) {m_ec = ec;}

  /// \brief Get the elliptic curve

  /// \return EC2N curve

  /// \details GetCurve() is not inherited

  const EC2N & GetCurve() const {return m_ec;}

private:

  EC2N m_ec;

};

NAMESPACE_END

#if CRYPTOPP_MSC_VERSION

# pragma warning(pop)

#endif

#endif