78 lines
1.8 KiB
C
78 lines
1.8 KiB
C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
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*
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* LibTomMath is a library that provides multiple-precision
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* integer arithmetic as well as number theoretic functionality.
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*
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* The library was designed directly after the MPI library by
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* Michael Fromberger but has been written from scratch with
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* additional optimizations in place.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@iahu.ca, http://math.libtomcrypt.org
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*/
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#include <tommath.h>
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/* performs a variable number of rounds of Miller-Rabin
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*
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* Probability of error after t rounds is no more than
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* (1/4)^t when 1 <= t <= PRIME_SIZE
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*
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* Sets result to 1 if probably prime, 0 otherwise
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*/
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int mp_prime_is_prime (mp_int * a, int t, int *result)
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{
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mp_int b;
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int ix, err, res;
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/* default to no */
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*result = MP_NO;
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/* valid value of t? */
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if (t <= 0 || t > PRIME_SIZE) {
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return MP_VAL;
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}
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/* is the input equal to one of the primes in the table? */
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for (ix = 0; ix < PRIME_SIZE; ix++) {
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if (mp_cmp_d(a, __prime_tab[ix]) == MP_EQ) {
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*result = 1;
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return MP_OKAY;
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}
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}
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/* first perform trial division */
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if ((err = mp_prime_is_divisible (a, &res)) != MP_OKAY) {
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return err;
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}
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/* return if it was trivially divisible */
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if (res == MP_YES) {
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return MP_OKAY;
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}
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/* now perform the miller-rabin rounds */
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if ((err = mp_init (&b)) != MP_OKAY) {
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return err;
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}
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for (ix = 0; ix < t; ix++) {
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/* set the prime */
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mp_set (&b, __prime_tab[ix]);
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if ((err = mp_prime_miller_rabin (a, &b, &res)) != MP_OKAY) {
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goto __B;
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}
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if (res == MP_NO) {
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goto __B;
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}
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}
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/* passed the test */
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*result = MP_YES;
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__B:mp_clear (&b);
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return err;
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}
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