Botan::Fixed_Window_Exponentiator Class Reference

#include <def_powm.h>

Inheritance diagram for Botan::Fixed_Window_Exponentiator:

Public Member Functions
Modular_Exponentiator *	copy () const
BigInt	execute () const
	Fixed_Window_Exponentiator (const BigInt &, Power_Mod::Usage_Hints)
void	set_base (const BigInt &)
void	set_exponent (const BigInt &)

Detailed Description

Fixed Window Exponentiator

Definition at line 20 of file def_powm.h.

Constructor & Destructor Documentation

Fixed_Window_Exponentiator()

Botan::Fixed_Window_Exponentiator::Fixed_Window_Exponentiator	(	const BigInt &	n,
		Power_Mod::Usage_Hints	hints )

Definition at line 61 of file powm_fw.cpp.

   {
   reducer = Modular_Reducer(n);
   this->hints = hints;
   window_bits = 0;
   }

References Botan::Modular_Reducer::Modular_Reducer().

Referenced by copy(), and Botan::Core_Engine::mod_exp().

Member Function Documentation

copy()

Modular_Exponentiator * Botan::Fixed_Window_Exponentiator::copy ( ) const

inlinevirtual

Implements Botan::Modular_Exponentiator.

Definition at line 27 of file def_powm.h.

         { return new Fixed_Window_Exponentiator(*this); }

References Fixed_Window_Exponentiator().

execute()

BigInt Botan::Fixed_Window_Exponentiator::execute ( ) const

virtual

Implements Botan::Modular_Exponentiator.

Definition at line 40 of file powm_fw.cpp.

   {
   const size_t exp_nibbles = (exp.bits() + window_bits - 1) / window_bits;
 
   BigInt x = 1;
 
   for(size_t i = exp_nibbles; i > 0; --i)
      {
      for(size_t j = 0; j != window_bits; ++j)
         x = reducer.square(x);
 
      const u32bit nibble = exp.get_substring(window_bits*(i-1), window_bits);
 
      x = reducer.multiply(x, g[nibble]);
      }
   return x;
   }

set_base()

void Botan::Fixed_Window_Exponentiator::set_base ( const BigInt & base )

virtual

Implements Botan::Modular_Exponentiator.

Definition at line 25 of file powm_fw.cpp.

   {
   window_bits = Power_Mod::window_bits(exp.bits(), base.bits(), hints);
 
   g.resize((1 << window_bits));
   g[0] = 1;
   g[1] = base;
 
   for(size_t i = 2; i != g.size(); ++i)
      g[i] = reducer.multiply(g[i-1], g[1]);
   }

References Botan::BigInt::bits(), and Botan::Power_Mod::window_bits().

set_exponent()

void Botan::Fixed_Window_Exponentiator::set_exponent ( const BigInt & e )

virtual

Implements Botan::Modular_Exponentiator.

Definition at line 17 of file powm_fw.cpp.

   {
   exp = e;
   }

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

• src/math/numbertheory/def_powm.h
• src/math/numbertheory/powm_fw.cpp