point_mul.h

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/*
* (C) 2018 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#ifndef BOTAN_POINT_MUL_H_
#define BOTAN_POINT_MUL_H_
 
#include <botan/ec_point.h>
 
namespace Botan {
 
class Barrett_Reduction;
 
class EC_Point_Base_Point_Precompute final {
   public:
      EC_Point_Base_Point_Precompute(const EC_Point& base_point, const Barrett_Reduction& mod_order);
 
      EC_Point mul(const BigInt& k,
                   RandomNumberGenerator& rng,
                   const BigInt& group_order,
                   std::vector<BigInt>& ws) const;
 
   private:
      const EC_Point& m_base_point;
      const Barrett_Reduction& m_mod_order;
 
      static constexpr size_t WindowBits = 3;
      static constexpr size_t WindowSize = (1 << WindowBits) - 1;
 
      const size_t m_p_words;
 
      /*
      * This is a table of T_size * 3*p_word words
      */
      std::vector<word> m_W;
};
 
class EC_Point_Var_Point_Precompute final {
   public:
      EC_Point_Var_Point_Precompute(const EC_Point& point, RandomNumberGenerator& rng, std::vector<BigInt>& ws);
 
      EC_Point mul(const BigInt& k,
                   RandomNumberGenerator& rng,
                   const BigInt& group_order,
                   std::vector<BigInt>& ws) const;
 
   private:
      static constexpr size_t WindowBits = 4;
 
      const CurveGFp m_curve;
      const size_t m_p_words;
 
      /*
      * Table of 2^window_bits * 3*2*p_word words
      * Kept in locked vector since the base point might be sensitive
      * (normally isn't in most protocols but hard to say anything
      * categorically.)
      */
      secure_vector<word> m_T;
};
 
class EC_Point_Multi_Point_Precompute final {
   public:
      EC_Point_Multi_Point_Precompute(const EC_Point& g1, const EC_Point& g2);
 
      /*
      * Return (g1*k1 + g2*k2)
      * Not constant time, intended to use with public inputs
      */
      EC_Point multi_exp(const BigInt& k1, const BigInt& k2) const;
 
   private:
      std::vector<EC_Point> m_M;
      bool m_no_infinity;
};
 
}  // namespace Botan
 
#endif