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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 CRYPTOPP_DLL 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 CRYPTOPP_DLL_TEMPLATE_CLASS AbstractGroup<ECPPoint>;
    00028
    00029 //! Elliptic Curve over GF(p), where p is prime
    00030 class CRYPTOPP_DLL ECP : public AbstractGroup<ECPPoint>
    00031 {
    00032 public:
    00033         typedef ModularArithmetic Field;
    00034         typedef Integer FieldElement;
    00035         typedef ECPPoint Point;
    00036
    00037         ECP() {}
    00038         ECP(const ECP &ecp, bool convertToMontgomeryRepresentation = false);
    00039         ECP(const Integer &modulus, const FieldElement &a, const FieldElement &b)
    00040                 : m_fieldPtr(new Field(modulus)), m_a(a.IsNegative() ? modulus+a : a), m_b(b) {}
    00041         // construct from BER encoded parameters
    00042         // this constructor will decode and extract the the fields fieldID and curve of the sequence ECParameters
    00043         ECP(BufferedTransformation &bt);
    00044
    00045         // encode the fields fieldID and curve of the sequence ECParameters
    00046         void DEREncode(BufferedTransformation &bt) const;
    00047
    00048         bool Equal(const Point &P, const Point &Q) const;
    00049         const Point& Identity() const;
    00050         const Point& Inverse(const Point &P) const;
    00051         bool InversionIsFast() const {return true;}
    00052         const Point& Add(const Point &P, const Point &Q) const;
    00053         const Point& Double(const Point &P) const;
    00054         Point ScalarMultiply(const Point &P, const Integer &k) const;
    00055         Point CascadeScalarMultiply(const Point &P, const Integer &k1, const Point &Q, const Integer &k2) const;
    00056         void SimultaneousMultiply(Point *results, const Point &base, const Integer *exponents, unsigned int exponentsCount) const;
    00057
    00058         Point Multiply(const Integer &k, const Point &P) const
    00059                 {return ScalarMultiply(P, k);}
    00060         Point CascadeMultiply(const Integer &k1, const Point &P, const Integer &k2, const Point &Q) const
    00061                 {return CascadeScalarMultiply(P, k1, Q, k2);}
    00062
    00063         bool ValidateParameters(RandomNumberGenerator &rng, unsigned int level=3) const;
    00064         bool VerifyPoint(const Point &P) const;
    00065
    00066         unsigned int EncodedPointSize(bool compressed = false) const
    00067                 {return 1 + (compressed?1:2)*GetField().MaxElementByteLength();}
    00068         // returns false if point is compressed and not valid (doesn't check if uncompressed)
    00069         bool DecodePoint(Point &P, BufferedTransformation &bt, size_t len) const;
    00070         bool DecodePoint(Point &P, const byte *encodedPoint, size_t len) const;
    00071         void EncodePoint(byte *encodedPoint, const Point &P, bool compressed) const;
    00072         void EncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const;
    00073
    00074         Point BERDecodePoint(BufferedTransformation &bt) const;
    00075         void DEREncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const;
    00076
    00077         Integer FieldSize() const {return GetField().GetModulus();}
    00078         const Field & GetField() const {return *m_fieldPtr;}
    00079         const FieldElement & GetA() const {return m_a;}
    00080         const FieldElement & GetB() const {return m_b;}
    00081
    00082         bool operator==(const ECP &rhs) const
    00083                 {return GetField() == rhs.GetField() && m_a == rhs.m_a && m_b == rhs.m_b;}
    00084
    00085 private:
    00086         clonable_ptr<Field> m_fieldPtr;
    00087         FieldElement m_a, m_b;
    00088         mutable Point m_R;
    00089 };
    00090
    00091 CRYPTOPP_DLL_TEMPLATE_CLASS DL_FixedBasePrecomputationImpl<ECP::Point>;
    00092 CRYPTOPP_DLL_TEMPLATE_CLASS DL_GroupPrecomputation<ECP::Point>;
    00093
    00094 template <class T> class EcPrecomputation;
    00095
    00096 //! ECP precomputation
    00097 template<> class EcPrecomputation<ECP> : public DL_GroupPrecomputation<ECP::Point>
    00098 {
    00099 public:
    00100         typedef ECP EllipticCurve;
    00101
    00102         // DL_GroupPrecomputation
    00103         bool NeedConversions() const {return true;}
    00104         Element ConvertIn(const Element &P) const
    00105                 {return P.identity ? P : ECP::Point(m_ec->GetField().ConvertIn(P.x), m_ec->GetField().ConvertIn(P.y));};
    00106         Element ConvertOut(const Element &P) const
    00107                 {return P.identity ? P : ECP::Point(m_ec->GetField().ConvertOut(P.x), m_ec->GetField().ConvertOut(P.y));}
    00108         const AbstractGroup<Element> & GetGroup() const {return *m_ec;}
    00109         Element BERDecodeElement(BufferedTransformation &bt) const {return m_ec->BERDecodePoint(bt);}
    00110         void DEREncodeElement(BufferedTransformation &bt, const Element &v) const {m_ec->DEREncodePoint(bt, v, false);}
    00111
    00112         // non-inherited
    00113         void SetCurve(const ECP &ec)
    00114         {
    00115                 m_ec.reset(new ECP(ec, true));
    00116                 m_ecOriginal = ec;
    00117         }
    00118         const ECP & GetCurve() const {return *m_ecOriginal;}
    00119
    00120 private:
    00121         value_ptr<ECP> m_ec, m_ecOriginal;
    00122 };
    00123
    00124 NAMESPACE_END
    00125
    00126 #endif