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/*
* Elliptic curves over GF(p)
*
* (C) 2007 Martin Doering, Christoph Ludwig, Falko Strenzke
* 2008 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/curve_gfp.h>
#include <botan/bigint.h>
#include <assert.h>
#include <ostream>
namespace Botan {
void CurveGFp::set_shrd_mod(const std::shared_ptr<GFpModulus> mod)
{
mp_mod = mod;
mA.turn_off_sp_red_mul();// m.m. is not needed, must be trf. back
mB.turn_off_sp_red_mul();// m.m. is not needed, must be trf. back
//ok, above we destroy any evantually computated montg. mult. values,
// but that won't influence performance in usual applications
mA.set_shrd_mod(mod);
mB.set_shrd_mod(mod);
}
CurveGFp::CurveGFp(const GFpElement& a, const GFpElement& b,
const BigInt& p)
: mA(a),
mB(b)
{
if(!((p == mA.get_p()) && (p == mB.get_p())))
{
throw Invalid_Argument("could not construct curve: moduli of arguments differ");
}
std::shared_ptr<GFpModulus> p_mod = std::shared_ptr<GFpModulus>(new GFpModulus(p));
// the above is the creation of the GFpModuls object which will be shared point-wide
// (in the context of a point of course)
set_shrd_mod(p_mod);
}
// copy constructor
CurveGFp::CurveGFp(const CurveGFp& other)
: mA(other.get_a()),
mB(other.get_b())
{
mp_mod = std::shared_ptr<GFpModulus>(new GFpModulus(*other.mp_mod));
assert(mp_mod->p_equal_to(mA.get_p()));
assert(mp_mod->p_equal_to(mB.get_p()));
set_shrd_mod(mp_mod);
if(other.mp_mres_a.get())
{
mp_mres_a = std::shared_ptr<GFpElement>(new GFpElement(*other.mp_mres_a));
}
if(other.mp_mres_b.get())
{
mp_mres_b = std::shared_ptr<GFpElement>(new GFpElement(*other.mp_mres_b));
}
if(other.mp_mres_one.get())
{
mp_mres_one = std::shared_ptr<GFpElement>(new GFpElement(*other.mp_mres_one));
}
}
// assignment operator
const CurveGFp& CurveGFp::operator=(const CurveGFp& other)
{
// for exception safety...
GFpElement a_tmp = other.mA;
GFpElement b_tmp = other.mB;
mA.swap(a_tmp);
mB.swap(b_tmp);
std::shared_ptr<GFpModulus> p_mod = std::shared_ptr<GFpModulus>(new GFpModulus(*other.mp_mod));
set_shrd_mod(p_mod);
// exception safety note: no problem if we have a throw from here on...
if(other.mp_mres_a.get())
{
mp_mres_a = std::shared_ptr<GFpElement>(new GFpElement(*other.mp_mres_a));
}
if(other.mp_mres_b.get())
{
mp_mres_b = std::shared_ptr<GFpElement>(new GFpElement(*other.mp_mres_b));
}
if(other.mp_mres_one.get())
{
mp_mres_one = std::shared_ptr<GFpElement>(new GFpElement(*other.mp_mres_one));
}
return *this;
}
// getters
const GFpElement& CurveGFp::get_a() const
{
return mA;
}
const GFpElement& CurveGFp::get_b() const
{
return mB;
}
const BigInt CurveGFp::get_p() const
{
assert(mp_mod.get() != 0);
return mp_mod->get_p();
}
// swaps the states of *this and other, does not throw
void CurveGFp::swap(CurveGFp& other)
{
mA.swap(other.mA);
mB.swap(other.mB);
mp_mod.swap(other.mp_mod);
std::swap(mp_mres_a, other.mp_mres_a);
std::swap(mp_mres_b, other.mp_mres_b);
std::swap(mp_mres_one, other.mp_mres_one);
}
GFpElement const CurveGFp::get_mres_a() const
{
if(mp_mres_a.get() == 0)
{
mp_mres_a = std::shared_ptr<GFpElement>(new GFpElement(mA));
mp_mres_a->turn_on_sp_red_mul();
mp_mres_a->get_mres();
}
return GFpElement(*mp_mres_a);
}
GFpElement const CurveGFp::get_mres_b() const
{
if(mp_mres_b.get() == 0)
{
mp_mres_b = std::shared_ptr<GFpElement>(new GFpElement(mB));
mp_mres_b->turn_on_sp_red_mul();
mp_mres_b->get_mres();
}
return GFpElement(*mp_mres_b);
}
std::shared_ptr<GFpElement const> const CurveGFp::get_mres_one() const
{
if(mp_mres_one.get() == 0)
{
mp_mres_one = std::shared_ptr<GFpElement>(new GFpElement(mp_mod->get_p(), 1));
mp_mres_one->turn_on_sp_red_mul();
mp_mres_one->get_mres();
}
return mp_mres_one;
}
bool operator==(const CurveGFp& lhs, const CurveGFp& rhs)
{
return (lhs.get_p() == rhs.get_p() && lhs.get_a() == rhs.get_a() && lhs.get_b() == rhs.get_b());
}
std::ostream& operator<<(std::ostream& output, const CurveGFp& elem)
{
return output << "y^2f = x^3 + (" << elem.get_a() << ")x + (" << elem.get_b() << ")";
}
}
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