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loop&shift until enough random data has been read

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This commit is contained in:
Steffen Jaeckel 2016-04-10 13:55:42 +02:00
parent 7cf5c050e2
commit d5b0f1e993
2 changed files with 21 additions and 6 deletions
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25
bn_mp_rand.c
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@ -15,15 +15,28 @@
* Tom St Denis, tstdenis82@gmail.com, http://libtom.org
*/
#if MP_GEN_RANDOM_MAX == 0xffffffff
#define MP_GEN_RANDOM_SHIFT 32
#elif MP_GEN_RANDOM_MAX == 32767
/* SHRT_MAX */
#define MP_GEN_RANDOM_SHIFT 15
#elif MP_GEN_RANDOM_MAX == 2147483647
/* INT_MAX */
#define MP_GEN_RANDOM_SHIFT 31
#elif !defined(MP_GEN_RANDOM_SHIFT)
#error Thou shalt define their own valid MP_GEN_RANDOM_SHIFT
#endif
/* makes a pseudo-random int of a given size */
static mp_digit mp_gen_random(void)
{
mp_digit d;
d = ((mp_digit) abs (MP_GEN_RANDOM()));
#if MP_DIGIT_BIT > 32
d <<= 32;
d |= ((mp_digit) abs (MP_GEN_RANDOM()));
#endif
mp_digit d = 0, msk = 0;
do {
d <<= MP_GEN_RANDOM_SHIFT;
d |= ((mp_digit) MP_GEN_RANDOM());
msk <<= MP_GEN_RANDOM_SHIFT;
msk |= MP_GEN_RANDOM_MAX;
} while ((MP_MASK & msk) != MP_MASK);
d &= MP_MASK;
return d;
}

2
tommath.h
View File

@ -102,8 +102,10 @@ extern "C" {
/* use arc4random on platforms that support it */
#ifdef MP_USE_ALT_RAND
#define MP_GEN_RANDOM() arc4random()
#define MP_GEN_RANDOM_MAX 0xffffffff
#else
#define MP_GEN_RANDOM() rand()
#define MP_GEN_RANDOM_MAX RAND_MAX
#endif
#define MP_DIGIT_BIT DIGIT_BIT