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ecp.h

00001 #ifndef CRYPTOPP_ECP_H
00002 #define CRYPTOPP_ECP_H
00003 
00004 #include "modarith.h"
00005 #include "eprecomp.h"
00006 #include "smartptr.h"
00007 #include "pubkey.h"
00008 
00009 NAMESPACE_BEGIN(CryptoPP)
00010 
00011 //! Elliptical Curve Point
00012 struct ECPPoint
00013 {
00014         ECPPoint() : identity(true) {}
00015         ECPPoint(const Integer &x, const Integer &y)
00016                 : identity(false), x(x), y(y) {}
00017 
00018         bool operator==(const ECPPoint &t) const
00019                 {return (identity && t.identity) || (!identity && !t.identity && x==t.x && y==t.y);}
00020         bool operator< (const ECPPoint &t) const
00021                 {return identity ? !t.identity : (!t.identity && (x<t.x || (x==t.x && y<t.y)));}
00022 
00023         bool identity;
00024         Integer x, y;
00025 };
00026 
00027 //! Elliptic Curve over GF(p), where p is prime
00028 class ECP : public AbstractGroup<ECPPoint>
00029 {
00030 public:
00031         typedef ModularArithmetic Field;
00032         typedef Integer FieldElement;
00033         typedef ECPPoint Point;
00034 
00035         ECP() {}
00036         ECP(const ECP &ecp, bool convertToMontgomeryRepresentation = false);
00037         ECP(const Integer &modulus, const FieldElement &a, const FieldElement &b)
00038                 : m_fieldPtr(new Field(modulus)), m_a(a.IsNegative() ? modulus+a : a), m_b(b) {}
00039         // construct from BER encoded parameters
00040         // this constructor will decode and extract the the fields fieldID and curve of the sequence ECParameters
00041         ECP(BufferedTransformation &bt);
00042 
00043         // encode the fields fieldID and curve of the sequence ECParameters
00044         void DEREncode(BufferedTransformation &bt) const;
00045 
00046         bool Equal(const Point &P, const Point &Q) const;
00047         const Point& Identity() const;
00048         const Point& Inverse(const Point &P) const;
00049         bool InversionIsFast() const {return true;}
00050         const Point& Add(const Point &P, const Point &Q) const;
00051         const Point& Double(const Point &P) const;
00052         Point ScalarMultiply(const Point &P, const Integer &k) const;
00053         Point CascadeScalarMultiply(const Point &P, const Integer &k1, const Point &Q, const Integer &k2) const;
00054         void SimultaneousMultiply(Point *results, const Point &base, const Integer *exponents, unsigned int exponentsCount) const;
00055 
00056         Point Multiply(const Integer &k, const Point &P) const
00057                 {return ScalarMultiply(P, k);}
00058         Point CascadeMultiply(const Integer &k1, const Point &P, const Integer &k2, const Point &Q) const
00059                 {return CascadeScalarMultiply(P, k1, Q, k2);}
00060 
00061         bool ValidateParameters(RandomNumberGenerator &rng, unsigned int level=3) const;
00062         bool VerifyPoint(const Point &P) const;
00063 
00064         unsigned int EncodedPointSize(bool compressed = false) const
00065                 {return 1 + (compressed?1:2)*GetField().MaxElementByteLength();}
00066         // returns false if point is compressed and not valid (doesn't check if uncompressed)
00067         bool DecodePoint(Point &P, BufferedTransformation &bt, unsigned int len) const;
00068         bool DecodePoint(Point &P, const byte *encodedPoint, unsigned int len) const;
00069         void EncodePoint(byte *encodedPoint, const Point &P, bool compressed) const;
00070         void EncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const;
00071 
00072         Point BERDecodePoint(BufferedTransformation &bt) const;
00073         void DEREncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const;
00074 
00075         Integer FieldSize() const {return GetField().GetModulus();}
00076         const Field & GetField() const {return *m_fieldPtr;}
00077         const FieldElement & GetA() const {return m_a;}
00078         const FieldElement & GetB() const {return m_b;}
00079 
00080 private:
00081         clonable_ptr<Field> m_fieldPtr;
00082         FieldElement m_a, m_b;
00083         mutable Point m_R;
00084 };
00085 
00086 template <class T> class EcPrecomputation;
00087 
00088 //! .
00089 template<> class EcPrecomputation<ECP> : public DL_GroupPrecomputation<ECP::Point>
00090 {
00091 public:
00092         typedef ECP EllipticCurve;
00093         
00094         // DL_GroupPrecomputation
00095         bool NeedConversions() const {return true;}
00096         Element ConvertIn(const Element &P) const
00097                 {return P.identity ? P : ECP::Point(m_ec->GetField().ConvertIn(P.x), m_ec->GetField().ConvertIn(P.y));};
00098         Element ConvertOut(const Element &P) const
00099                 {return P.identity ? P : ECP::Point(m_ec->GetField().ConvertOut(P.x), m_ec->GetField().ConvertOut(P.y));}
00100         const AbstractGroup<Element> & GetGroup() const {return *m_ec;}
00101         Element BERDecodeElement(BufferedTransformation &bt) const {return m_ec->BERDecodePoint(bt);}
00102         void DEREncodeElement(BufferedTransformation &bt, const Element &v) const {m_ec->DEREncodePoint(bt, v, false);}
00103 
00104         // non-inherited
00105         void SetCurve(const ECP &ec);
00106         const ECP & GetCurve() const {return *m_ecOriginal;}
00107 
00108 private:
00109         value_ptr<ECP> m_ec, m_ecOriginal;
00110 };
00111 
00112 NAMESPACE_END
00113 
00114 #endif

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