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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 #ifndef SKIP_EXPLICIT_INSTANTIATION
00028 CRYPTOPP_DLL_TEMPLATE_CLASS AbstractGroup<ECPPoint>;
00029 #endif // SKIP_EXPLICIT_INSTANTIATION
00030 
00031 //! Elliptic Curve over GF(p), where p is prime
00032 class CRYPTOPP_DLL ECP : public AbstractGroup<ECPPoint>
00033 {
00034 public:
00035         typedef ModularArithmetic Field;
00036         typedef Integer FieldElement;
00037         typedef ECPPoint Point;
00038 
00039         ECP() {}
00040         ECP(const ECP &ecp, bool convertToMontgomeryRepresentation = false);
00041         ECP(const Integer &modulus, const FieldElement &a, const FieldElement &b)
00042                 : m_fieldPtr(new Field(modulus)), m_a(a.IsNegative() ? modulus+a : a), m_b(b) {}
00043         // construct from BER encoded parameters
00044         // this constructor will decode and extract the the fields fieldID and curve of the sequence ECParameters
00045         ECP(BufferedTransformation &bt);
00046 
00047         // encode the fields fieldID and curve of the sequence ECParameters
00048         void DEREncode(BufferedTransformation &bt) const;
00049 
00050         bool Equal(const Point &P, const Point &Q) const;
00051         const Point& Identity() const;
00052         const Point& Inverse(const Point &P) const;
00053         bool InversionIsFast() const {return true;}
00054         const Point& Add(const Point &P, const Point &Q) const;
00055         const Point& Double(const Point &P) const;
00056         Point ScalarMultiply(const Point &P, const Integer &k) const;
00057         Point CascadeScalarMultiply(const Point &P, const Integer &k1, const Point &Q, const Integer &k2) const;
00058         void SimultaneousMultiply(Point *results, const Point &base, const Integer *exponents, unsigned int exponentsCount) const;
00059 
00060         Point Multiply(const Integer &k, const Point &P) const
00061                 {return ScalarMultiply(P, k);}
00062         Point CascadeMultiply(const Integer &k1, const Point &P, const Integer &k2, const Point &Q) const
00063                 {return CascadeScalarMultiply(P, k1, Q, k2);}
00064 
00065         bool ValidateParameters(RandomNumberGenerator &rng, unsigned int level=3) const;
00066         bool VerifyPoint(const Point &P) const;
00067 
00068         unsigned int EncodedPointSize(bool compressed = false) const
00069                 {return 1 + (compressed?1:2)*GetField().MaxElementByteLength();}
00070         // returns false if point is compressed and not valid (doesn't check if uncompressed)
00071         bool DecodePoint(Point &P, BufferedTransformation &bt, size_t len) const;
00072         bool DecodePoint(Point &P, const byte *encodedPoint, size_t len) const;
00073         void EncodePoint(byte *encodedPoint, const Point &P, bool compressed) const;
00074         void EncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const;
00075 
00076         Point BERDecodePoint(BufferedTransformation &bt) const;
00077         void DEREncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const;
00078 
00079         Integer FieldSize() const {return GetField().GetModulus();}
00080         const Field & GetField() const {return *m_fieldPtr;}
00081         const FieldElement & GetA() const {return m_a;}
00082         const FieldElement & GetB() const {return m_b;}
00083 
00084         bool operator==(const ECP &rhs) const
00085                 {return GetField() == rhs.GetField() && m_a == rhs.m_a && m_b == rhs.m_b;}
00086 
00087 private:
00088         clonable_ptr<Field> m_fieldPtr;
00089         FieldElement m_a, m_b;
00090         mutable Point m_R;
00091 };
00092 
00093 #ifndef SKIP_EXPLICIT_INSTANTIATION
00094 CRYPTOPP_DLL_TEMPLATE_CLASS DL_FixedBasePrecomputationImpl<ECP::Point>;
00095 CRYPTOPP_DLL_TEMPLATE_CLASS DL_GroupPrecomputation<ECP::Point>;
00096 #endif // SKIP_EXPLICIT_INSTANTIATION
00097 
00098 template <class T> class EcPrecomputation;
00099 
00100 //! ECP precomputation
00101 template<> class EcPrecomputation<ECP> : public DL_GroupPrecomputation<ECP::Point>
00102 {
00103 public:
00104         typedef ECP EllipticCurve;
00105         
00106         // DL_GroupPrecomputation
00107         bool NeedConversions() const {return true;}
00108         Element ConvertIn(const Element &P) const
00109                 {return P.identity ? P : ECP::Point(m_ec->GetField().ConvertIn(P.x), m_ec->GetField().ConvertIn(P.y));};
00110         Element ConvertOut(const Element &P) const
00111                 {return P.identity ? P : ECP::Point(m_ec->GetField().ConvertOut(P.x), m_ec->GetField().ConvertOut(P.y));}
00112         const AbstractGroup<Element> & GetGroup() const {return *m_ec;}
00113         Element BERDecodeElement(BufferedTransformation &bt) const {return m_ec->BERDecodePoint(bt);}
00114         void DEREncodeElement(BufferedTransformation &bt, const Element &v) const {m_ec->DEREncodePoint(bt, v, false);}
00115 
00116         // non-inherited
00117         void SetCurve(const ECP &ec)
00118         {
00119                 m_ec.reset(new ECP(ec, true));
00120                 m_ecOriginal = ec;
00121         }
00122         const ECP & GetCurve() const {return *m_ecOriginal;}
00123 
00124 private:
00125         value_ptr<ECP> m_ec, m_ecOriginal;
00126 };
00127 
00128 NAMESPACE_END
00129 
00130 #endif

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