big_rand.cpp

含有多种公开密钥算法、多种块加密、多种数据流加密、多种HASH函数、多种CheckSum校验、多种MAC校验等几十种加密算法的程序

/*************************************************
* Random BigInt Generation Source File           *
* (C) 1999-2002 The Botan Project                *
*************************************************/

#include <botan/numthry.h>
#include <botan/primes.h>

namespace Botan {

/*************************************************
* Generate a random integer                      *
*************************************************/
BigInt random_integer(u32bit bits)
   {
   BigInt x;
   x.randomize(bits);
   return x;
   }

/*************************************************
* Generate a random integer within given range   *
*************************************************/
BigInt random_integer(const BigInt& min, const BigInt& max)
   {
   BigInt range = max - min;

   if(range <= 0)
      throw Invalid_Argument("random_integer: invalid min/max values");

   return (min + (random_integer(range.bits() + 1) % range));
   }

/*************************************************
* Generate a random prime                        *
*************************************************/
BigInt random_prime(u32bit bits, const BigInt& coprime)
   {
   if(bits <= 16)
      throw Invalid_Argument("random_prime: Can't make a prime of " +
                             to_string(bits) + " bits");
   if(coprime <= 0)
      throw Invalid_Argument("random_prime: comprime must be > 0");

   while(true)
      {
      BigInt p(Random, bits);
      p.set_bit(bits - 2);
      p.set_bit(0);

      SecureVector<u32bit> sieve(100);

      for(u32bit j = 0; j != sieve.size(); j++)
         sieve[j] = p % PRIMES[j];

      u32bit counter = 0;
      while(true)
         {
         if(counter == 4096 || p.bits() > bits)
            break;

         bool passes_sieve = true;
         counter++;
         p += 2;

         for(u32bit j = 0; j != sieve.size(); j++)
            {
            sieve[j] = (sieve[j] + 2) % PRIMES[j];
            if(sieve[j] == 0)
               passes_sieve = false;
            }

         if(!passes_sieve || gcd(p - BigInt::one(), coprime) != BigInt::one())
            continue;
         if(passes_mr_tests(p))
            return p;
         }
      }
   }

/*************************************************
* Generate a random safe prime                   *
*************************************************/
BigInt random_safe_prime(u32bit bits)
   {
   if(bits <= 16)
      throw Invalid_Argument("random_safe_prime: Can't make a prime of " +
                             to_string(bits) + " bits");

   BigInt p;
   do
      p = (random_prime(bits - 1) << 1) + BigInt::one();
   while(!is_prime(p));
   return p;
   }

}