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Diffstat (limited to 'src/math/ec_gfp/point_gfp.h')
| -rw-r--r-- | src/math/ec_gfp/point_gfp.h | 262 |
1 files changed, 262 insertions, 0 deletions
diff --git a/src/math/ec_gfp/point_gfp.h b/src/math/ec_gfp/point_gfp.h new file mode 100644 index 000000000..8c279dbd1 --- /dev/null +++ b/src/math/ec_gfp/point_gfp.h @@ -0,0 +1,262 @@ +/* +* Point arithmetic on elliptic curves over GF(p) +* +* (C) 2007 Martin Doering, Christoph Ludwig, Falko Strenzke +* 2008-2011 Jack Lloyd +* +* Distributed under the terms of the Botan license +*/ + +#ifndef BOTAN_POINT_GFP_H__ +#define BOTAN_POINT_GFP_H__ + +#include <botan/curve_gfp.h> +#include <vector> + +namespace Botan { + +/** +* Exception thrown if you try to convert a zero point to an affine +* coordinate +*/ +struct BOTAN_DLL Illegal_Transformation : public Exception + { + Illegal_Transformation(const std::string& err = + "Requested transformation is not possible") : + Exception(err) {} + }; + +/** +* Exception thrown if some form of illegal point is decoded +*/ +struct BOTAN_DLL Illegal_Point : public Exception + { + Illegal_Point(const std::string& err = "Malformed ECP point detected") : + Exception(err) {} + }; + +/** +* This class represents one point on a curve of GF(p) +*/ +class BOTAN_DLL PointGFp + { + public: + enum Compression_Type { + UNCOMPRESSED = 0, + COMPRESSED = 1, + HYBRID = 2 + }; + + /** + * Construct an uninitialized PointGFp + */ + PointGFp() {} + + /** + * Construct the zero point + * @param curve The base curve + */ + PointGFp(const CurveGFp& curve); + + /** + * Construct a point from its affine coordinates + * @param curve the base curve + * @param x affine x coordinate + * @param y affine y coordinate + */ + PointGFp(const CurveGFp& curve, const BigInt& x, const BigInt& y); + + //PointGFp(const PointGFp& other) = default; + //PointGFp& operator=(const PointGFp& other) = default; + + /** + * += Operator + * @param rhs the PointGFp to add to the local value + * @result resulting PointGFp + */ + PointGFp& operator+=(const PointGFp& rhs); + + /** + * -= Operator + * @param rhs the PointGFp to subtract from the local value + * @result resulting PointGFp + */ + PointGFp& operator-=(const PointGFp& rhs); + + /** + * *= Operator + * @param scalar the PointGFp to multiply with *this + * @result resulting PointGFp + */ + PointGFp& operator*=(const BigInt& scalar); + + /** + * Multiplication Operator + * @param scalar the scalar value + * @param point the point value + * @return scalar*point on the curve + */ + friend BOTAN_DLL PointGFp operator*(const BigInt& scalar, const PointGFp& point); + + /** + * Negate this point + * @return *this + */ + PointGFp& negate() + { + if(!is_zero()) + coord_y = curve.get_p() - coord_y; + return *this; + } + + /** + * Return base curve of this point + * @result the curve over GF(p) of this point + */ + const CurveGFp& get_curve() const { return curve; } + + /** + * get affine x coordinate + * @result affine x coordinate + */ + BigInt get_affine_x() const; + + /** + * get affine y coordinate + * @result affine y coordinate + */ + BigInt get_affine_y() const; + + /** + * Is this the point at infinity? + * @result true, if this point is at infinity, false otherwise. + */ + bool is_zero() const + { return (coord_x.is_zero() && coord_z.is_zero()); } + + /** + * Checks whether the point is to be found on the underlying + * curve; used to prevent fault attacks. + * @return if the point is on the curve + */ + bool on_the_curve() const; + + /** + * swaps the states of *this and other, does not throw! + * @param other the object to swap values with + */ + void swap(PointGFp& other); + + /** + * Equality operator + */ + bool operator==(const PointGFp& other) const; + private: + + /** + * Montgomery multiplication/reduction + * @param x first multiplicand + * @param y second multiplicand + * @param workspace temp space + */ + BigInt monty_mult(const BigInt& x, const BigInt& y) const + { + BigInt result; + monty_mult(result, x, y); + return result; + } + + /** + * Montgomery multiplication/reduction + * @warning z cannot alias x or y + * @param z output + * @param x first multiplicand + * @param y second multiplicand + */ + void monty_mult(BigInt& z, const BigInt& x, const BigInt& y) const; + + /** + * Montgomery squaring/reduction + * @param x multiplicand + */ + BigInt monty_sqr(const BigInt& x) const + { + BigInt result; + monty_sqr(result, x); + return result; + } + + /** + * Montgomery squaring/reduction + * @warning z cannot alias x + * @param z output + * @param x multiplicand + */ + void monty_sqr(BigInt& z, const BigInt& x) const; + + /** + * Point addition + * @param workspace temp space, at least 11 elements + */ + void add(const PointGFp& other, std::vector<BigInt>& workspace); + + /** + * Point doubling + * @param workspace temp space, at least 9 elements + */ + void mult2(std::vector<BigInt>& workspace); + + CurveGFp curve; + BigInt coord_x, coord_y, coord_z; + mutable SecureVector<word> ws; // workspace for Montgomery + }; + +// relational operators +inline bool operator!=(const PointGFp& lhs, const PointGFp& rhs) + { + return !(rhs == lhs); + } + +// arithmetic operators +inline PointGFp operator-(const PointGFp& lhs) + { + return PointGFp(lhs).negate(); + } + +inline PointGFp operator+(const PointGFp& lhs, const PointGFp& rhs) + { + PointGFp tmp(lhs); + return tmp += rhs; + } + +inline PointGFp operator-(const PointGFp& lhs, const PointGFp& rhs) + { + PointGFp tmp(lhs); + return tmp -= rhs; + } + +inline PointGFp operator*(const PointGFp& point, const BigInt& scalar) + { + return scalar * point; + } + +// encoding and decoding +SecureVector<byte> BOTAN_DLL EC2OSP(const PointGFp& point, byte format); + +PointGFp BOTAN_DLL OS2ECP(const byte data[], size_t data_len, + const CurveGFp& curve); + +inline PointGFp OS2ECP(const MemoryRegion<byte>& data, const CurveGFp& curve) + { return OS2ECP(&data[0], data.size(), curve); } + +} + +namespace std { + +template<> +inline void swap<Botan::PointGFp>(Botan::PointGFp& x, Botan::PointGFp& y) + { x.swap(y); } + +} + +#endif |