51 lines
1.2 KiB
C
51 lines
1.2 KiB
C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
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*
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* LibTomMath is library that provides for multiple-precision
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* integer arithmetic as well as number theoretic functionality.
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*
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* The library is 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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/* determines if an integers is divisible by one of the first 256 primes or not
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*
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* sets result to 0 if not, 1 if yes
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*/
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int
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mp_prime_is_divisible (mp_int * a, int *result)
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{
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int err, ix;
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mp_digit res;
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/* default to not */
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*result = 0;
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for (ix = 0; ix < 256; ix++) {
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/* is it equal to the prime? */
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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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/* what is a mod __prime_tab[ix] */
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if ((err = mp_mod_d (a, __prime_tab[ix], &res)) != MP_OKAY) {
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return err;
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}
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/* is the residue zero? */
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if (res == 0) {
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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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return MP_OKAY;
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}
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