Botan::PointGFp_Multi_Point_Precompute Class Reference

#include <point_mul.h>

Public Member Functions
PointGFp	multi_exp (const BigInt &k1, const BigInt &k2) const
	PointGFp_Multi_Point_Precompute (const PointGFp &g1, const PointGFp &g2)

Detailed Description

Definition at line 67 of file point_mul.h.

Constructor & Destructor Documentation

Botan::PointGFp_Multi_Point_Precompute::PointGFp_Multi_Point_Precompute	(	const PointGFp &	g1,
		const PointGFp &	g2
	)

Definition at line 340 of file point_mul.cpp.

References Botan::PointGFp::force_all_affine(), Botan::PointGFp::mult2(), Botan::PointGFp::plus(), and Botan::PointGFp::WORKSPACE_SIZE.

   {
   std::vector<BigInt> ws(PointGFp::WORKSPACE_SIZE);

   PointGFp x2 = x;
   x2.mult2(ws);

   const PointGFp x3(x2.plus(x, ws));

   PointGFp y2 = y;
   y2.mult2(ws);

   const PointGFp y3(y2.plus(y, ws));

   m_M.reserve(15);

   m_M.push_back(x);
   m_M.push_back(x2);
   m_M.push_back(x3);

   m_M.push_back(y);
   m_M.push_back(y.plus(x, ws));
   m_M.push_back(y.plus(x2, ws));
   m_M.push_back(y.plus(x3, ws));

   m_M.push_back(y2);
   m_M.push_back(y2.plus(x, ws));
   m_M.push_back(y2.plus(x2, ws));
   m_M.push_back(y2.plus(x3, ws));

   m_M.push_back(y3);
   m_M.push_back(y3.plus(x, ws));
   m_M.push_back(y3.plus(x2, ws));
   m_M.push_back(y3.plus(x3, ws));

   PointGFp::force_all_affine(m_M, ws[0].get_word_vector());
   }

Member Function Documentation

PointGFp Botan::PointGFp_Multi_Point_Precompute::multi_exp	(	const BigInt &	k1,
		const BigInt &	k2
	)		const

Definition at line 379 of file point_mul.cpp.

References Botan::PointGFp::add_affine(), Botan::BigInt::bits(), Botan::BigInt::get_substring(), Botan::BigInt::is_negative(), Botan::PointGFp::mult2i(), Botan::PointGFp::negate(), Botan::round_up(), and Botan::PointGFp::WORKSPACE_SIZE.

Referenced by Botan::multi_exponentiate(), and Botan::EC_Group::point_multiply().

   {
   std::vector<BigInt> ws(PointGFp::WORKSPACE_SIZE);

   const size_t z_bits = round_up(std::max(z1.bits(), z2.bits()), 2);

   PointGFp H = m_M[0].zero();

   for(size_t i = 0; i != z_bits; i += 2)
      {
      if(i > 0)
         {
         H.mult2i(2, ws);
         }

      const uint32_t z1_b = z1.get_substring(z_bits - i - 2, 2);
      const uint32_t z2_b = z2.get_substring(z_bits - i - 2, 2);

      const uint32_t z12 = (4*z2_b) + z1_b;

      // This function is not intended to be const time
      if(z12)
         {
         H.add_affine(m_M[z12-1], ws);
         }
      }

   if(z1.is_negative() != z2.is_negative())
      H.negate();

   return H;
   }

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The documentation for this class was generated from the following files:

• src/lib/pubkey/ec_group/point_mul.h
• src/lib/pubkey/ec_group/point_mul.cpp