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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 CRYPTOPP_DLL_TEMPLATE_CLASS AbstractGroup<EC2NPoint>;
00028 
00029 //! Elliptic Curve over GF(2^n)
00030 class CRYPTOPP_DLL EC2N : public AbstractGroup<EC2NPoint>
00031 {
00032 public:
00033     typedef GF2NP Field;
00034     typedef Field::Element FieldElement;
00035     typedef EC2NPoint Point;
00036 
00037     EC2N() {}
00038     EC2N(const Field &field, const Field::Element &a, const Field::Element &b)
00039         : m_field(field), m_a(a), m_b(b) {}
00040     // construct from BER encoded parameters
00041     // this constructor will decode and extract the the fields fieldID and curve of the sequence ECParameters
00042     EC2N(BufferedTransformation &bt);
00043 
00044     // encode the fields fieldID and curve of the sequence ECParameters
00045     void DEREncode(BufferedTransformation &bt) const;
00046 
00047     bool Equal(const Point &P, const Point &Q) const;
00048     const Point& Identity() const;
00049     const Point& Inverse(const Point &P) const;
00050     bool InversionIsFast() const {return true;}
00051     const Point& Add(const Point &P, const Point &Q) const;
00052     const Point& Double(const Point &P) const;
00053 
00054     Point Multiply(const Integer &k, const Point &P) const
00055         {return ScalarMultiply(P, k);}
00056     Point CascadeMultiply(const Integer &k1, const Point &P, const Integer &k2, const Point &Q) const
00057         {return CascadeScalarMultiply(P, k1, Q, k2);}
00058 
00059     bool ValidateParameters(RandomNumberGenerator &rng, unsigned int level=3) const;
00060     bool VerifyPoint(const Point &P) const;
00061 
00062     unsigned int EncodedPointSize(bool compressed = false) const
00063         {return 1 + (compressed?1:2)*m_field->MaxElementByteLength();}
00064     // returns false if point is compressed and not valid (doesn't check if uncompressed)
00065     bool DecodePoint(Point &P, BufferedTransformation &bt, size_t len) const;
00066     bool DecodePoint(Point &P, const byte *encodedPoint, size_t len) const;
00067     void EncodePoint(byte *encodedPoint, const Point &P, bool compressed) const;
00068     void EncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const;
00069 
00070     Point BERDecodePoint(BufferedTransformation &bt) const;
00071     void DEREncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const;
00072 
00073     Integer FieldSize() const {return Integer::Power2(m_field->MaxElementBitLength());}
00074     const Field & GetField() const {return *m_field;}
00075     const FieldElement & GetA() const {return m_a;}
00076     const FieldElement & GetB() const {return m_b;}
00077 
00078     bool operator==(const EC2N &rhs) const
00079         {return GetField() == rhs.GetField() && m_a == rhs.m_a && m_b == rhs.m_b;}
00080 
00081 private:
00082     clonable_ptr<Field> m_field;
00083     FieldElement m_a, m_b;
00084     mutable Point m_R;
00085 };
00086 
00087 CRYPTOPP_DLL_TEMPLATE_CLASS DL_FixedBasePrecomputationImpl<EC2N::Point>;
00088 CRYPTOPP_DLL_TEMPLATE_CLASS DL_GroupPrecomputation<EC2N::Point>;
00089 
00090 template <class T> class EcPrecomputation;
00091 
00092 //! EC2N precomputation
00093 template<> class EcPrecomputation<EC2N> : public DL_GroupPrecomputation<EC2N::Point>
00094 {
00095 public:
00096     typedef EC2N EllipticCurve;
00097 
00098     // DL_GroupPrecomputation
00099     const AbstractGroup<Element> & GetGroup() const {return m_ec;}
00100     Element BERDecodeElement(BufferedTransformation &bt) const {return m_ec.BERDecodePoint(bt);}
00101     void DEREncodeElement(BufferedTransformation &bt, const Element &v) const {m_ec.DEREncodePoint(bt, v, false);}
00102 
00103     // non-inherited
00104     void SetCurve(const EC2N &ec) {m_ec = ec;}
00105     const EC2N & GetCurve() const {return m_ec;}
00106 
00107 private:
00108     EC2N m_ec;
00109 };
00110 
00111 NAMESPACE_END
00112 
00113 #endif

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