Botan::Power_Mod Class Reference

#include <pow_mod.h>

Inheritance diagram for Botan::Power_Mod:

Public Types
enum	Usage_Hints {   NO_HINTS = 0x0000, BASE_IS_FIXED = 0x0001, BASE_IS_SMALL = 0x0002, BASE_IS_LARGE = 0x0004,   BASE_IS_2 = 0x0008, EXP_IS_FIXED = 0x0100, EXP_IS_SMALL = 0x0200, EXP_IS_LARGE = 0x0400 }

Public Member Functions
BigInt	execute () const
Power_Mod &	operator= (const Power_Mod &)
	Power_Mod (const BigInt &modulus=0, Usage_Hints hints=NO_HINTS, bool disable_montgomery_arith=false)
	Power_Mod (const Power_Mod &)
void	set_base (const BigInt &base) const
void	set_exponent (const BigInt &exponent) const
void	set_modulus (const BigInt &modulus, Usage_Hints hints=NO_HINTS, bool disable_montgomery_arith=false) const
virtual	~Power_Mod ()=default

Static Public Member Functions
static size_t	window_bits (size_t exp_bits, size_t base_bits, Power_Mod::Usage_Hints hints)

Detailed Description

Modular Exponentiator Proxy

Definition at line 35 of file pow_mod.h.

Member Enumeration Documentation

Usage_Hints

enum Botan::Power_Mod::Usage_Hints

Enumerator
NO_HINTS
BASE_IS_FIXED
BASE_IS_SMALL
BASE_IS_LARGE
BASE_IS_2
EXP_IS_FIXED
EXP_IS_SMALL
EXP_IS_LARGE

Definition at line 39 of file pow_mod.h.

                       {
         NO_HINTS        = 0x0000,

         BASE_IS_FIXED   = 0x0001,
         BASE_IS_SMALL   = 0x0002,
         BASE_IS_LARGE   = 0x0004,
         BASE_IS_2       = 0x0008,

         EXP_IS_FIXED    = 0x0100,
         EXP_IS_SMALL    = 0x0200,
         EXP_IS_LARGE    = 0x0400
      };

Constructor & Destructor Documentation

Power_Mod() [1/2]

Botan::Power_Mod::Power_Mod	(	const BigInt &	modulus = 0,
		Usage_Hints	hints = NO_HINTS,
		bool	disable_montgomery_arith = false
	)

Parameters

modulus	Optionally call set_modulus
hints	Passed to set_modulus if modulus > 0
disable_montgomery_arith	Disables use of Montgomery representation. Likely only useful for testing.

Definition at line 16 of file pow_mod.cpp.

References set_modulus().

   {
   set_modulus(n, hints, disable_monty);
   }

Power_Mod() [2/2]

Botan::Power_Mod::Power_Mod

(

const Power_Mod &

other

)

Definition at line 24 of file pow_mod.cpp.

   {
   if(other.m_core.get())
      m_core.reset(other.m_core->copy());
   }

~Power_Mod()

virtual Botan::Power_Mod::~Power_Mod ( )

virtualdefault

Member Function Documentation

execute()

BigInt Botan::Power_Mod::execute

(

)

const

All three of the above functions must have already been called.

Returns

result of g^xp

Definition at line 92 of file pow_mod.cpp.

Referenced by Botan::power_mod().

   {
   if(!m_core)
      throw Internal_Error("Power_Mod::execute: m_core was NULL");
   return m_core->execute();
   }

operator=()

Power_Mod & Botan::Power_Mod::operator=

(

const Power_Mod &

other

)

Definition at line 33 of file pow_mod.cpp.

   {
   if(this != &other)
      {
      if(other.m_core)
         m_core.reset(other.m_core->copy());
      else
         m_core.reset();
      }
   return (*this);
   }

set_base()

void Botan::Power_Mod::set_base

(

const BigInt &

base

)

const

Set the base

Definition at line 66 of file pow_mod.cpp.

References Botan::BigInt::is_negative(), and Botan::BigInt::is_zero().

Referenced by Botan::Fixed_Base_Power_Mod::Fixed_Base_Power_Mod(), and Botan::power_mod().

   {
   if(b.is_zero() || b.is_negative())
      throw Invalid_Argument("Power_Mod::set_base: arg must be > 0");

   if(!m_core)
      throw Internal_Error("Power_Mod::set_base: m_core was NULL");
   m_core->set_base(b);
   }

set_exponent()

void Botan::Power_Mod::set_exponent

(

const BigInt &

exponent

)

const

Set the exponent

Definition at line 79 of file pow_mod.cpp.

References Botan::BigInt::is_negative().

Referenced by Botan::Fixed_Exponent_Power_Mod::Fixed_Exponent_Power_Mod(), and Botan::power_mod().

   {
   if(e.is_negative())
      throw Invalid_Argument("Power_Mod::set_exponent: arg must be > 0");

   if(!m_core)
      throw Internal_Error("Power_Mod::set_exponent: m_core was NULL");
   m_core->set_exponent(e);
   }

set_modulus()

void Botan::Power_Mod::set_modulus	(	const BigInt &	modulus,
		Usage_Hints	hints = NO_HINTS,
		bool	disable_montgomery_arith = false
	)		const

Parameters

modulus	the modulus
hints	Passed to set_modulus if modulus > 0
disable_montgomery_arith	Disables use of Montgomery representation. Likely only useful for testing.

Definition at line 48 of file pow_mod.cpp.

References Botan::BigInt::is_odd().

Referenced by Power_Mod().

   {
   // Allow set_modulus(0) to mean "drop old state"

   m_core.reset();

   if(n != 0)
      {
      if(n.is_odd() && disable_monty == false)
         m_core.reset(new Montgomery_Exponentiator(n, hints));
      else
         m_core.reset(new Fixed_Window_Exponentiator(n, hints));
      }
   }

window_bits()

size_t Botan::Power_Mod::window_bits ( size_t  exp_bits, size_t  base_bits, Power_Mod::Usage_Hints  hints  )

static

Definition at line 102 of file pow_mod.cpp.

References BASE_IS_FIXED, and EXP_IS_LARGE.

Referenced by Botan::Fixed_Window_Exponentiator::set_base(), and Botan::Montgomery_Exponentiator::set_base().

   {
   static const size_t wsize[][2] = {
      { 1434, 7 },
      {  539, 6 },
      {  197, 4 },
      {   70, 3 },
      {   17, 2 },
      {    0, 0 }
   };

   size_t window_bits = 1;

   if(exp_bits)
      {
      for(size_t j = 0; wsize[j][0]; ++j)
         {
         if(exp_bits >= wsize[j][0])
            {
            window_bits += wsize[j][1];
            break;
            }
         }
      }

   if(hints & Power_Mod::BASE_IS_FIXED)
      window_bits += 2;
   if(hints & Power_Mod::EXP_IS_LARGE)
      ++window_bits;

   return window_bits;
   }

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

• src/lib/math/numbertheory/pow_mod.h
• src/lib/math/numbertheory/pow_mod.cpp