ecpoint.h

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// ecpoint.h - written and placed in the public domain by Jeffrey Walton
//             Data structures moved from ecp.h and ec2n.h. Added EncodedPoint interface
 
/// \file ecpoint.h
/// \brief Classes for Elliptic Curve points
/// \since Crypto++ 6.0
 
#ifndef CRYPTOPP_ECPOINT_H
#define CRYPTOPP_ECPOINT_H
 
#include "cryptlib.h"
#include "integer.h"
#include "algebra.h"
#include "gf2n.h"
 
NAMESPACE_BEGIN(CryptoPP)
 
/// \brief Elliptical Curve Point over GF(p), where p is prime
/// \since Crypto++ 2.0
struct CRYPTOPP_DLL ECPPoint
{
    virtual ~ECPPoint() {}
 
    /// \brief Construct an ECPPoint
    /// \details identity is set to <tt>true</tt>
    ECPPoint() : identity(true) {}
 
    /// \brief Construct an ECPPoint from coordinates
    /// \details identity is set to <tt>false</tt>
    ECPPoint(const Integer &x, const Integer &y)
        : x(x), y(y), identity(false) {}
 
    /// \brief Tests points for equality
    /// \param t the other point
    /// \return true if the points are equal, false otherwise
    bool operator==(const ECPPoint &t) const
        {return (identity && t.identity) || (!identity && !t.identity && x==t.x && y==t.y);}
 
    /// \brief Tests points for ordering
    /// \param t the other point
    /// \return true if this point is less than other, false otherwise
    bool operator< (const ECPPoint &t) const
        {return identity ? !t.identity : (!t.identity && (x<t.x || (x==t.x && y<t.y)));}
 
    Integer x, y;
    bool identity;
};
 
CRYPTOPP_DLL_TEMPLATE_CLASS AbstractGroup<ECPPoint>;
 
/// \brief Elliptical Curve Point over GF(2^n)
/// \since Crypto++ 2.0
struct CRYPTOPP_DLL EC2NPoint
{
    virtual ~EC2NPoint() {}
 
    /// \brief Construct an EC2NPoint
    /// \details identity is set to <tt>true</tt>
    EC2NPoint() : identity(true) {}
 
    /// \brief Construct an EC2NPoint from coordinates
    /// \details identity is set to <tt>false</tt>
    EC2NPoint(const PolynomialMod2 &x, const PolynomialMod2 &y)
        : x(x), y(y), identity(false) {}
 
    /// \brief Tests points for equality
    /// \param t the other point
    /// \return true if the points are equal, false otherwise
    bool operator==(const EC2NPoint &t) const
        {return (identity && t.identity) || (!identity && !t.identity && x==t.x && y==t.y);}
 
    /// \brief Tests points for ordering
    /// \param t the other point
    /// \return true if this point is less than other, false otherwise
    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>;
 
/// \brief Abstract class for encoding and decoding ellicptic curve points
/// \tparam Point ellicptic curve point
/// \details EncodedPoint is an interface for encoding and decoding elliptic curve points.
///   The template parameter <tt>Point</tt> should be a class like ECP or EC2N.
/// \since Crypto++ 6.0
template <class Point>
class EncodedPoint
{
public:
    virtual ~EncodedPoint() {}
 
    /// \brief Decodes an elliptic curve point
    /// \param P point which is decoded
    /// \param bt source BufferedTransformation
    /// \param len number of bytes to read from the BufferedTransformation
    /// \return true if a point was decoded, false otherwise
    virtual bool DecodePoint(Point &P, BufferedTransformation &bt, size_t len) const =0;
 
    /// \brief Decodes an elliptic curve point
    /// \param P point which is decoded
    /// \param encodedPoint byte array with the encoded point
    /// \param len the size of the array
    /// \return true if a point was decoded, false otherwise
    virtual bool DecodePoint(Point &P, const byte *encodedPoint, size_t len) const =0;
 
    /// \brief Verifies points on elliptic curve
    /// \param P point to verify
    /// \return true if the point is valid, false otherwise
    virtual bool VerifyPoint(const Point &P) const =0;
 
    /// \brief Determines encoded point size
    /// \param compressed flag indicating if the point is compressed
    /// \return the minimum number of bytes required to encode the point
    virtual unsigned int EncodedPointSize(bool compressed = false) const =0;
 
    /// \brief Encodes an elliptic curve point
    /// \param P point which is decoded
    /// \param encodedPoint byte array for the encoded point
    /// \param compressed flag indicating if the point is compressed
    /// \details <tt>encodedPoint</tt> must be at least EncodedPointSize() in length
    virtual void EncodePoint(byte *encodedPoint, const Point &P, bool compressed) const =0;
 
    /// \brief Encodes an elliptic curve point
    /// \param bt target BufferedTransformation
    /// \param P point which is encoded
    /// \param compressed flag indicating if the point is compressed
    virtual void EncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const =0;
 
    /// \brief BER Decodes an elliptic curve point
    /// \param bt source BufferedTransformation
    /// \return the decoded elliptic curve point
    virtual Point BERDecodePoint(BufferedTransformation &bt) const =0;
 
    /// \brief DER Encodes an elliptic curve point
    /// \param bt target BufferedTransformation
    /// \param P point which is encoded
    /// \param compressed flag indicating if the point is compressed
    virtual void DEREncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const =0;
};
 
NAMESPACE_END
 
#endif  // CRYPTOPP_ECPOINT_H