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ec2n.h

00001 #ifndef CRYPTOPP_EC2N_H
00002 #define CRYPTOPP_EC2N_H
00003 
00004 #include "gf2n.h"
00005 #include "eprecomp.h"
00006 #include "smartptr.h"
00007 #include "pubkey.h"
00008 
00009 NAMESPACE_BEGIN(CryptoPP)
00010 
00011 //! Elliptic Curve Point
00012 struct CRYPTOPP_DLL EC2NPoint
00013 {
00014         EC2NPoint() : identity(true) {}
00015         EC2NPoint(const PolynomialMod2 &x, const PolynomialMod2 &y)
00016                 : identity(false), x(x), y(y) {}
00017 
00018         bool operator==(const EC2NPoint &t) const
00019                 {return (identity && t.identity) || (!identity && !t.identity && x==t.x && y==t.y);}
00020         bool operator< (const EC2NPoint &t) const
00021                 {return identity ? !t.identity : (!t.identity && (x<t.x || (x==t.x && y<t.y)));}
00022 
00023         bool identity;
00024         PolynomialMod2 x, y;
00025 };
00026 
00027 #ifndef SKIP_EXPLICIT_INSTANTIATION
00028 CRYPTOPP_DLL_TEMPLATE_CLASS AbstractGroup<EC2NPoint>;
00029 #endif // SKIP_EXPLICIT_INSTANTIATION
00030 
00031 //! Elliptic Curve over GF(2^n)
00032 class CRYPTOPP_DLL EC2N : public AbstractGroup<EC2NPoint>
00033 {
00034 public:
00035         typedef GF2NP Field;
00036         typedef Field::Element FieldElement;
00037         typedef EC2NPoint Point;
00038 
00039         EC2N() {}
00040         EC2N(const Field &field, const Field::Element &a, const Field::Element &b)
00041                 : m_field(field), m_a(a), m_b(b) {}
00042         // construct from BER encoded parameters
00043         // this constructor will decode and extract the the fields fieldID and curve of the sequence ECParameters
00044         EC2N(BufferedTransformation &bt);
00045 
00046         // encode the fields fieldID and curve of the sequence ECParameters
00047         void DEREncode(BufferedTransformation &bt) const;
00048 
00049         bool Equal(const Point &P, const Point &Q) const;
00050         const Point& Identity() const;
00051         const Point& Inverse(const Point &P) const;
00052         bool InversionIsFast() const {return true;}
00053         const Point& Add(const Point &P, const Point &Q) const;
00054         const Point& Double(const Point &P) 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)*m_field->MaxElementByteLength();}
00066         // returns false if point is compressed and not valid (doesn't check if uncompressed)
00067         bool DecodePoint(Point &P, BufferedTransformation &bt, size_t len) const;
00068         bool DecodePoint(Point &P, const byte *encodedPoint, size_t 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 Integer::Power2(m_field->MaxElementBitLength());}
00076         const Field & GetField() const {return *m_field;}
00077         const FieldElement & GetA() const {return m_a;}
00078         const FieldElement & GetB() const {return m_b;}
00079 
00080         bool operator==(const EC2N &rhs) const
00081                 {return GetField() == rhs.GetField() && m_a == rhs.m_a && m_b == rhs.m_b;}
00082 
00083 private:
00084         clonable_ptr<Field> m_field;
00085         FieldElement m_a, m_b;
00086         mutable Point m_R;
00087 };
00088 
00089 #ifndef SKIP_EXPLICIT_INSTANTIATION
00090 CRYPTOPP_DLL_TEMPLATE_CLASS DL_FixedBasePrecomputationImpl<EC2N::Point>;
00091 CRYPTOPP_DLL_TEMPLATE_CLASS DL_GroupPrecomputation<EC2N::Point>;
00092 #endif
00093 
00094 template <class T> class EcPrecomputation;
00095 
00096 //! EC2N precomputation
00097 template<> class EcPrecomputation<EC2N> : public DL_GroupPrecomputation<EC2N::Point>
00098 {
00099 public:
00100         typedef EC2N EllipticCurve;
00101 
00102         // DL_GroupPrecomputation
00103         const AbstractGroup<Element> & GetGroup() const {return m_ec;}
00104         Element BERDecodeElement(BufferedTransformation &bt) const {return m_ec.BERDecodePoint(bt);}
00105         void DEREncodeElement(BufferedTransformation &bt, const Element &v) const {m_ec.DEREncodePoint(bt, v, false);}
00106 
00107         // non-inherited
00108         void SetCurve(const EC2N &ec) {m_ec = ec;}
00109         const EC2N & GetCurve() const {return m_ec;}
00110 
00111 private:
00112         EC2N m_ec;
00113 };
00114 
00115 NAMESPACE_END
00116 
00117 #endif

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