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/* 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
* additional optimizations in place.
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, tomstdenis@iahu.ca, http://math.libtomcrypt.org
*/
#include <tommath.h>
/* performs a variable number of rounds of Miller-Rabin
*
* Probability of error after t rounds is no more than
* (1/4)^t when 1 <= t <= PRIME_SIZE
*
* 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, __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, __prime_tab[ix]);
if ((err = mp_prime_miller_rabin (a, &b, &res)) != MP_OKAY) {
goto __B;
}
if (res == MP_NO) {
goto __B;
}
}
/* passed the test */
*result = MP_YES;
__B:mp_clear (&b);
return err;
}
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