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add FP_GEN_RANDOM logic as in libtommath

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This commit is contained in:
Steffen Jaeckel 2017-03-30 16:15:35 +02:00
parent 637dfe6d44
commit 8e034dcf6e
2 changed files with 39 additions and 2 deletions
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13
src/headers/tfm.h
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@ -252,6 +252,19 @@
#endif
#endif
/* platforms that can use a better rand function */
#if defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__NetBSD__) || defined(__DragonFly__)
#define FP_USE_ALT_RAND 1
#endif
/* use arc4random on platforms that support it */
#ifdef FP_USE_ALT_RAND
#define FP_GEN_RANDOM() arc4random()
#define FP_GEN_RANDOM_MAX 0xffffffff
#else
#define FP_GEN_RANDOM() rand()
#define FP_GEN_RANDOM_MAX RAND_MAX
#endif
/* some default configurations.
*/

28
src/misc/fp_rand.c
View File

@ -9,7 +9,31 @@
*/
#include <tfm_private.h>
#if FP_GEN_RANDOM_MAX == 0xffffffff
#define FP_GEN_RANDOM_SHIFT 32
#elif FP_GEN_RANDOM_MAX == 32767
/* SHRT_MAX */
#define FP_GEN_RANDOM_SHIFT 15
#elif FP_GEN_RANDOM_MAX == 2147483647
/* INT_MAX */
#define FP_GEN_RANDOM_SHIFT 31
#elif !defined(FP_GEN_RANDOM_SHIFT)
#error Thou shalt define their own valid FP_GEN_RANDOM_SHIFT
#endif
/* makes a pseudo-random int of a given size */
static fp_digit fp_gen_random(void)
{
fp_digit d = 0, msk = 0;
do {
d <<= FP_GEN_RANDOM_SHIFT;
d |= ((fp_digit) FP_GEN_RANDOM());
msk <<= FP_GEN_RANDOM_SHIFT;
msk |= FP_GEN_RANDOM_MAX;
} while ((FP_MASK & msk) != FP_MASK);
d &= FP_MASK;
return d;
}
void fp_rand(fp_int *a, int digits)
{
@ -22,14 +46,14 @@ void fp_rand(fp_int *a, int digits)
/* first place a random non-zero digit */
do {
d = ((fp_digit) abs (rand ())) & FP_MASK;
d = fp_gen_random();
} while (d == 0);
fp_add_d (a, d, a);
while (--digits > 0) {
fp_lshd (a, 1);
fp_add_d (a, ((fp_digit) abs (rand ())), a);
fp_add_d (a, fp_gen_random(), a);
}
return;