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ecp.h

#ifndef CRYPTOPP_ECP_H
#define CRYPTOPP_ECP_H

#include "modarith.h"
#include "eprecomp.h"
#include "smartptr.h"

NAMESPACE_BEGIN(CryptoPP)

struct ECPPoint
{
        ECPPoint() : identity(true) {}
        ECPPoint(const Integer &x, const Integer &y)
                : identity(false), x(x), y(y) {}

        bool operator==(const ECPPoint &t) const
                {return (identity && t.identity) || (!identity && !t.identity && x==t.x && y==t.y);}
        bool operator< (const ECPPoint &t) const
                {return identity ? !t.identity : (!t.identity && (x<t.x || (x==t.x && y<t.y)));}

        bool identity;
        Integer x, y;
};

class ECP : public AbstractGroup<ECPPoint>
{
public:
        typedef ModularArithmetic Field;
        typedef Integer FieldElement;
        typedef ECPPoint Point;

        ECP(const ECP &ecp)
                : m_fieldPtr(new Field(ecp.m_field.GetModulus())), m_field(*m_fieldPtr), m_a(ecp.m_a), m_b(ecp.m_b) {}
        ECP(const Integer &modulus, const FieldElement &a, const FieldElement &b)
                : m_fieldPtr(new Field(modulus)), m_field(*m_fieldPtr), m_a(a.IsNegative() ? modulus+a : a), m_b(b) {}
        ECP(const MontgomeryRepresentation &mr, const FieldElement &a, const FieldElement &b)
                : m_field(mr), 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
        ECP(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& Zero() const {static const Point zero; return zero;}
        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 ScalarMultiply(const Point &P, const Integer &k) const;
        Point CascadeScalarMultiply(const Point &P, const Integer &k1, const Point &Q, const Integer &k2) const;
        void SimultaneousMultiply(Point *results, const Point &base, const Integer *exponents, unsigned int exponentsCount) 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) 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, unsigned int len) const;
        bool DecodePoint(Point &P, const byte *encodedPoint, unsigned int len) const;
        void EncodePoint(byte *encodedPoint, const Point &P, bool compressed = false) const;

        Point BERDecodePoint(BufferedTransformation &bt) const;
        void DEREncodePoint(BufferedTransformation &bt, const Point &P, bool compressed = false) const;

        Integer FieldSize() const {return m_field.GetModulus();}
        const Field & GetField() const {return m_field;}
        const FieldElement & GetA() const {return m_a;}
        const FieldElement & GetB() const {return m_b;}

private:
        member_ptr<Field> m_fieldPtr;
        const Field &m_field;
        FieldElement m_a, m_b;
        mutable Point m_R;
};

template <class T> class EcPrecomputation;

template<> class EcPrecomputation<ECP>
{
public:
        EcPrecomputation() {}
        EcPrecomputation(const EcPrecomputation &a)
                {operator=(a);}
        EcPrecomputation(const ECP &ec, const ECP::Point &base)
                {SetCurveAndBase(ec, base);}

        EcPrecomputation& operator=(const EcPrecomputation &rhs);

        void SetCurveAndBase(const ECP &ec, const ECP::Point &base);
        void Precompute(unsigned int maxExpBits, unsigned int storage);
        void Load(BufferedTransformation &storedPrecomputation);
        void Save(BufferedTransformation &storedPrecomputation) const;

        ECP::Point Multiply(const Integer &exponent) const;
        ECP::Point CascadeMultiply(const Integer &exponent, const EcPrecomputation<ECP> &pc2, const Integer &exponent2) const;

private:
        value_ptr<MontgomeryRepresentation> m_mr;
        value_ptr<ECP> m_ec;
        ExponentiationPrecomputation<ECP::Point> m_ep;
};

NAMESPACE_END

#endif

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