### view libtommath/bn_mp_prime_is_prime.c @ 389:5ff8218bcee9

author Matt Johnston Thu, 11 Jan 2007 03:14:55 +0000 eed26cff980b 60fc6476e044
line wrap: on
line source
```#include <tommath.h>
#ifdef BN_MP_PRIME_IS_PRIME_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
*
* LibTomMath is a library that provides multiple-precision
* integer arithmetic as well as number theoretic functionality.
*
* The library was designed directly after the MPI library by
* Michael Fromberger but has been written from scratch with
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, [email protected], http://math.libtomcrypt.com
*/

/* performs a variable number of rounds of Miller-Rabin
*
* Probability of error after t rounds is no more than

*
* Sets result to 1 if probably prime, 0 otherwise
*/
int mp_prime_is_prime (mp_int * a, int t, int *result)
{
mp_int  b;
int     ix, err, res;

/* default to no */
*result = MP_NO;

/* valid value of t? */
if (t <= 0 || t > PRIME_SIZE) {
return MP_VAL;
}

/* is the input equal to one of the primes in the table? */
for (ix = 0; ix < PRIME_SIZE; ix++) {
if (mp_cmp_d(a, ltm_prime_tab[ix]) == MP_EQ) {
*result = 1;
return MP_OKAY;
}
}

/* first perform trial division */
if ((err = mp_prime_is_divisible (a, &res)) != MP_OKAY) {
return err;
}

/* return if it was trivially divisible */
if (res == MP_YES) {
return MP_OKAY;
}

/* now perform the miller-rabin rounds */
if ((err = mp_init (&b)) != MP_OKAY) {
return err;
}

for (ix = 0; ix < t; ix++) {
/* set the prime */
mp_set (&b, ltm_prime_tab[ix]);

if ((err = mp_prime_miller_rabin (a, &b, &res)) != MP_OKAY) {
goto LBL_B;
}

if (res == MP_NO) {
goto LBL_B;
}
}

/* passed the test */
*result = MP_YES;
LBL_B:mp_clear (&b);
return err;
}
#endif

/* \$Source: /cvs/libtom/libtommath/bn_mp_prime_is_prime.c,v \$ */
/* \$Revision: 1.3 \$ */
/* \$Date: 2006/03/31 14:18:44 \$ */
```