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/*
* BigInt Random Generation
* (C) 1999-2007 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/bigint.h>
#include <botan/rng.h>
#include <botan/internal/rounding.h>
namespace Botan {
/*
* Randomize this number
*/
void BigInt::randomize(RandomNumberGenerator& rng,
size_t bitsize, bool set_high_bit)
{
set_sign(Positive);
if(bitsize == 0)
{
clear();
}
else
{
secure_vector<uint8_t> array = rng.random_vec(round_up(bitsize, 8) / 8);
// Always cut unwanted bits
if(bitsize % 8)
array[0] &= 0xFF >> (8 - (bitsize % 8));
// Set the highest bit if wanted
if (set_high_bit)
array[0] |= 0x80 >> ((bitsize % 8) ? (8 - bitsize % 8) : 0);
binary_decode(array);
}
}
/*
* Generate a random integer within given range
*/
BigInt BigInt::random_integer(RandomNumberGenerator& rng,
const BigInt& min, const BigInt& max)
{
if(min.is_negative() || max.is_negative() || max <= min)
throw Invalid_Argument("BigInt::random_integer invalid range");
BigInt r;
const size_t bits = max.bits();
do
{
r.randomize(rng, bits, false);
}
while(r < min || r >= max);
return r;
}
}