55 lines
1.3 KiB
C
55 lines
1.3 KiB
C
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/* 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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/* finds the next prime after the number "a" using "t" trials
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* of Miller-Rabin.
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*/
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int mp_prime_next_prime(mp_int *a, int t)
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{
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int err, res;
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if (mp_iseven(a) == 1) {
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/* force odd */
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if ((err = mp_add_d(a, 1, a)) != MP_OKAY) {
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return err;
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}
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} else {
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/* force to next number */
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if ((err = mp_add_d(a, 2, a)) != MP_OKAY) {
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return err;
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}
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}
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for (;;) {
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/* is this prime? */
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if ((err = mp_prime_is_prime(a, t, &res)) != MP_OKAY) {
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return err;
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}
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if (res == 1) {
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break;
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}
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/* add two, next candidate */
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if ((err = mp_add_d(a, 2, a)) != MP_OKAY) {
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return err;
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}
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}
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return MP_OKAY;
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}
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