largePrimeGenerator Class Reference

Generate n-bit prime numbers. More...

#include <primegen.h>

Collaboration diagram for largePrimeGenerator:

List of all members.

Public Member Functions
	largePrimeGenerator ()
	Constructor generates a small prime table.
	~largePrimeGenerator ()
void	findprime_sequentially (ZZ &n, uintc nbits) const
void	findprime_randomly (ZZ &n, uintc nbits) const
	Keep looking for primes randomly till one found.
bool const	isprime (ZZ const &n) const
	Statistical prime test.
void	ensurenbits (ZZ &n, uintc nbits) const
	n is >= 2^nbits.

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Detailed Description

Generate n-bit prime numbers.

The library could do many of these functions but these functions are so easily to implement that another library could be easily used instead, so the library calls are isolated.

ie ZZ could be templated, random bit generation implemented and prime testing implemented then the only dependency is ZZ.

Definition at line 21 of file primegen.h.

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Constructor & Destructor Documentation

largePrimeGenerator::largePrimeGenerator

(

)

Constructor generates a small prime table.

Definition at line 64 of file primegen.cpp.

  : v(0), vmax(1000)
{
  PrimeSeq s;

  v = new long int [vmax];

  for (uint i=0; i<vmax; ++i)
    v[i] = s.next();
}

largePrimeGenerator::~largePrimeGenerator

(

)

Definition at line 75 of file primegen.cpp.

{
  delete[] v;
  v=0;
}

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Member Function Documentation

void largePrimeGenerator::ensurenbits	(	ZZ &	n,
		uintc	nbits
	)			const

n is >= 2^nbits.

Definition at line 7 of file primegen.cpp.

{
  ZZ n2;
  ZZ x;
  conv(x,"2"); 
  power(n2,x,nbits);
  if (n<n2)
    n += n2;
 
  if ((n%2)==0)
    ++n;
}

void largePrimeGenerator::findprime_randomly	(	ZZ &	n,
		uintc	nbits
	)			const

Keep looking for primes randomly till one found.

Definition at line 21 of file primegen.cpp.

Referenced by rsaGenKey::rsaGenKey(), and rsatest::test02().

{
  for ( ; ; )
  {
    RandomBits(n,nbits);
    ensurenbits(n,nbits);
    if (isprime(n))
      return;
  }
}

void largePrimeGenerator::findprime_sequentially	(	ZZ &	n,
		uintc	nbits
	)			const

Definition at line 37 of file primegen.cpp.

Referenced by rsatest::test02().

{
  RandomBits(n,nbits);
  ensurenbits(n,nbits);

  for ( ; ; )
  {
    if (isprime(n))
      return;

    n += 2;
  }
}

bool const largePrimeGenerator::isprime

(

ZZ const &

n

)

const

Statistical prime test.

Do not use with small primes.

Definition at line 54 of file primegen.cpp.

{
  for (uint i=0; i<vmax; ++i)
    if ((n%v[i])==0)
      return false;

  return ProbPrime(n,15);
}

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

• rsa/primegen.h
• rsa/primegen.cpp