diff options
Diffstat (limited to 'libtommath/bn_mp_prime_miller_rabin.c')
| -rw-r--r-- | libtommath/bn_mp_prime_miller_rabin.c | 138 |
1 files changed, 69 insertions, 69 deletions
diff --git a/libtommath/bn_mp_prime_miller_rabin.c b/libtommath/bn_mp_prime_miller_rabin.c index 7de0634..18eba8c 100644 --- a/libtommath/bn_mp_prime_miller_rabin.c +++ b/libtommath/bn_mp_prime_miller_rabin.c @@ -1,4 +1,4 @@ -#include <tommath_private.h> +#include "tommath_private.h" #ifdef BN_MP_PRIME_MILLER_RABIN_C /* LibTomMath, multiple-precision integer library -- Tom St Denis * @@ -9,95 +9,95 @@ * 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, tstdenis82@gmail.com, http://libtom.org + * SPDX-License-Identifier: Unlicense */ -/* Miller-Rabin test of "a" to the base of "b" as described in +/* Miller-Rabin test of "a" to the base of "b" as described in * HAC pp. 139 Algorithm 4.24 * * Sets result to 0 if definitely composite or 1 if probably prime. - * Randomly the chance of error is no more than 1/4 and often + * Randomly the chance of error is no more than 1/4 and often * very much lower. */ -int mp_prime_miller_rabin (mp_int * a, mp_int * b, int *result) +int mp_prime_miller_rabin(const mp_int *a, const mp_int *b, int *result) { - mp_int n1, y, r; - int s, j, err; + mp_int n1, y, r; + int s, j, err; + + /* default */ + *result = MP_NO; - /* default */ - *result = MP_NO; + /* ensure b > 1 */ + if (mp_cmp_d(b, 1uL) != MP_GT) { + return MP_VAL; + } - /* ensure b > 1 */ - if (mp_cmp_d(b, 1) != MP_GT) { - return MP_VAL; - } + /* get n1 = a - 1 */ + if ((err = mp_init_copy(&n1, a)) != MP_OKAY) { + return err; + } + if ((err = mp_sub_d(&n1, 1uL, &n1)) != MP_OKAY) { + goto LBL_N1; + } - /* get n1 = a - 1 */ - if ((err = mp_init_copy (&n1, a)) != MP_OKAY) { - return err; - } - if ((err = mp_sub_d (&n1, 1, &n1)) != MP_OKAY) { - goto LBL_N1; - } + /* set 2**s * r = n1 */ + if ((err = mp_init_copy(&r, &n1)) != MP_OKAY) { + goto LBL_N1; + } - /* set 2**s * r = n1 */ - if ((err = mp_init_copy (&r, &n1)) != MP_OKAY) { - goto LBL_N1; - } + /* count the number of least significant bits + * which are zero + */ + s = mp_cnt_lsb(&r); - /* count the number of least significant bits - * which are zero - */ - s = mp_cnt_lsb(&r); + /* now divide n - 1 by 2**s */ + if ((err = mp_div_2d(&r, s, &r, NULL)) != MP_OKAY) { + goto LBL_R; + } - /* now divide n - 1 by 2**s */ - if ((err = mp_div_2d (&r, s, &r, NULL)) != MP_OKAY) { - goto LBL_R; - } + /* compute y = b**r mod a */ + if ((err = mp_init(&y)) != MP_OKAY) { + goto LBL_R; + } + if ((err = mp_exptmod(b, &r, a, &y)) != MP_OKAY) { + goto LBL_Y; + } - /* compute y = b**r mod a */ - if ((err = mp_init (&y)) != MP_OKAY) { - goto LBL_R; - } - if ((err = mp_exptmod (b, &r, a, &y)) != MP_OKAY) { - goto LBL_Y; - } + /* if y != 1 and y != n1 do */ + if ((mp_cmp_d(&y, 1uL) != MP_EQ) && (mp_cmp(&y, &n1) != MP_EQ)) { + j = 1; + /* while j <= s-1 and y != n1 */ + while ((j <= (s - 1)) && (mp_cmp(&y, &n1) != MP_EQ)) { + if ((err = mp_sqrmod(&y, a, &y)) != MP_OKAY) { + goto LBL_Y; + } - /* if y != 1 and y != n1 do */ - if ((mp_cmp_d (&y, 1) != MP_EQ) && (mp_cmp (&y, &n1) != MP_EQ)) { - j = 1; - /* while j <= s-1 and y != n1 */ - while ((j <= (s - 1)) && (mp_cmp (&y, &n1) != MP_EQ)) { - if ((err = mp_sqrmod (&y, a, &y)) != MP_OKAY) { - goto LBL_Y; + /* if y == 1 then composite */ + if (mp_cmp_d(&y, 1uL) == MP_EQ) { + goto LBL_Y; + } + + ++j; } - /* if y == 1 then composite */ - if (mp_cmp_d (&y, 1) == MP_EQ) { + /* if y != n1 then composite */ + if (mp_cmp(&y, &n1) != MP_EQ) { goto LBL_Y; } + } - ++j; - } - - /* if y != n1 then composite */ - if (mp_cmp (&y, &n1) != MP_EQ) { - goto LBL_Y; - } - } - - /* probably prime now */ - *result = MP_YES; -LBL_Y:mp_clear (&y); -LBL_R:mp_clear (&r); -LBL_N1:mp_clear (&n1); - return err; + /* probably prime now */ + *result = MP_YES; +LBL_Y: + mp_clear(&y); +LBL_R: + mp_clear(&r); +LBL_N1: + mp_clear(&n1); + return err; } #endif -/* ref: $Format:%D$ */ -/* git commit: $Format:%H$ */ -/* commit time: $Format:%ai$ */ +/* ref: HEAD -> master, tag: v1.1.0 */ +/* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */ +/* commit time: 2019-01-28 20:32:32 +0100 */ |