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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

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