diff options
Diffstat (limited to 'libtommath/bn_mp_prime_next_prime.c')
| -rw-r--r-- | libtommath/bn_mp_prime_next_prime.c | 140 |
1 files changed, 51 insertions, 89 deletions
diff --git a/libtommath/bn_mp_prime_next_prime.c b/libtommath/bn_mp_prime_next_prime.c index 7a32d9b..d656565 100644 --- a/libtommath/bn_mp_prime_next_prime.c +++ b/libtommath/bn_mp_prime_next_prime.c @@ -1,70 +1,42 @@ -#include <tommath_private.h> +#include "tommath_private.h" #ifdef BN_MP_PRIME_NEXT_PRIME_C -/* 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, tstdenis82@gmail.com, http://libtom.org - */ +/* LibTomMath, multiple-precision integer library -- Tom St Denis */ +/* SPDX-License-Identifier: Unlicense */ /* finds the next prime after the number "a" using "t" trials * of Miller-Rabin. * * bbs_style = 1 means the prime must be congruent to 3 mod 4 */ -int mp_prime_next_prime(mp_int *a, int t, int bbs_style) +mp_err mp_prime_next_prime(mp_int *a, int t, int bbs_style) { - int err, res = MP_NO, x, y; - mp_digit res_tab[PRIME_SIZE], step, kstep; + int x, y; + mp_ord cmp; + mp_err err; + mp_bool res = MP_NO; + mp_digit res_tab[PRIVATE_MP_PRIME_TAB_SIZE], step, kstep; mp_int b; - /* ensure t is valid */ - if ((t <= 0) || (t > PRIME_SIZE)) { - return MP_VAL; - } - /* force positive */ a->sign = MP_ZPOS; /* simple algo if a is less than the largest prime in the table */ - if (mp_cmp_d(a, ltm_prime_tab[PRIME_SIZE-1]) == MP_LT) { - /* find which prime it is bigger than */ - for (x = PRIME_SIZE - 2; x >= 0; x--) { - if (mp_cmp_d(a, ltm_prime_tab[x]) != MP_LT) { - if (bbs_style == 1) { - /* ok we found a prime smaller or - * equal [so the next is larger] - * - * however, the prime must be - * congruent to 3 mod 4 - */ - if ((ltm_prime_tab[x + 1] & 3) != 3) { - /* scan upwards for a prime congruent to 3 mod 4 */ - for (y = x + 1; y < PRIME_SIZE; y++) { - if ((ltm_prime_tab[y] & 3) == 3) { - mp_set(a, ltm_prime_tab[y]); - return MP_OKAY; - } - } - } - } else { - mp_set(a, ltm_prime_tab[x + 1]); - return MP_OKAY; - } - } - } - /* at this point a maybe 1 */ - if (mp_cmp_d(a, 1) == MP_EQ) { - mp_set(a, 2); - return MP_OKAY; + if (mp_cmp_d(a, s_mp_prime_tab[PRIVATE_MP_PRIME_TAB_SIZE-1]) == MP_LT) { + /* find which prime it is bigger than "a" */ + for (x = 0; x < PRIVATE_MP_PRIME_TAB_SIZE; x++) { + cmp = mp_cmp_d(a, s_mp_prime_tab[x]); + if (cmp == MP_EQ) { + continue; + } + if (cmp != MP_GT) { + if ((bbs_style == 1) && ((s_mp_prime_tab[x] & 3u) != 3u)) { + /* try again until we get a prime congruent to 3 mod 4 */ + continue; + } else { + mp_set(a, s_mp_prime_tab[x]); + return MP_OKAY; + } + } } /* fall through to the sieve */ } @@ -80,21 +52,23 @@ int mp_prime_next_prime(mp_int *a, int t, int bbs_style) if (bbs_style == 1) { /* if a mod 4 != 3 subtract the correct value to make it so */ - if ((a->dp[0] & 3) != 3) { - if ((err = mp_sub_d(a, (a->dp[0] & 3) + 1, a)) != MP_OKAY) { return err; }; + if ((a->dp[0] & 3u) != 3u) { + if ((err = mp_sub_d(a, (a->dp[0] & 3u) + 1u, a)) != MP_OKAY) { + return err; + } } } else { - if (mp_iseven(a) == MP_YES) { + if (MP_IS_EVEN(a)) { /* force odd */ - if ((err = mp_sub_d(a, 1, a)) != MP_OKAY) { + if ((err = mp_sub_d(a, 1uL, a)) != MP_OKAY) { return err; } } } /* generate the restable */ - for (x = 1; x < PRIME_SIZE; x++) { - if ((err = mp_mod_d(a, ltm_prime_tab[x], res_tab + x)) != MP_OKAY) { + for (x = 1; x < PRIVATE_MP_PRIME_TAB_SIZE; x++) { + if ((err = mp_mod_d(a, s_mp_prime_tab[x], res_tab + x)) != MP_OKAY) { return err; } } @@ -115,43 +89,35 @@ int mp_prime_next_prime(mp_int *a, int t, int bbs_style) step += kstep; /* compute the new residue without using division */ - for (x = 1; x < PRIME_SIZE; x++) { - /* add the step to each residue */ - res_tab[x] += kstep; - - /* subtract the modulus [instead of using division] */ - if (res_tab[x] >= ltm_prime_tab[x]) { - res_tab[x] -= ltm_prime_tab[x]; - } - - /* set flag if zero */ - if (res_tab[x] == 0) { - y = 1; - } + for (x = 1; x < PRIVATE_MP_PRIME_TAB_SIZE; x++) { + /* add the step to each residue */ + res_tab[x] += kstep; + + /* subtract the modulus [instead of using division] */ + if (res_tab[x] >= s_mp_prime_tab[x]) { + res_tab[x] -= s_mp_prime_tab[x]; + } + + /* set flag if zero */ + if (res_tab[x] == 0u) { + y = 1; + } } - } while ((y == 1) && (step < ((((mp_digit)1) << DIGIT_BIT) - kstep))); + } while ((y == 1) && (step < (((mp_digit)1 << MP_DIGIT_BIT) - kstep))); /* add the step */ if ((err = mp_add_d(a, step, a)) != MP_OKAY) { goto LBL_ERR; } - /* if didn't pass sieve and step == MAX then skip test */ - if ((y == 1) && (step >= ((((mp_digit)1) << DIGIT_BIT) - kstep))) { + /* if didn't pass sieve and step == MP_MAX then skip test */ + if ((y == 1) && (step >= (((mp_digit)1 << MP_DIGIT_BIT) - kstep))) { continue; } - /* is this prime? */ - for (x = 0; x < t; x++) { - mp_set(&b, ltm_prime_tab[x]); - if ((err = mp_prime_miller_rabin(a, &b, &res)) != MP_OKAY) { - goto LBL_ERR; - } - if (res == MP_NO) { - break; - } + if ((err = mp_prime_is_prime(a, t, &res)) != MP_OKAY) { + goto LBL_ERR; } - if (res == MP_YES) { break; } @@ -164,7 +130,3 @@ LBL_ERR: } #endif - -/* ref: $Format:%D$ */ -/* git commit: $Format:%H$ */ -/* commit time: $Format:%ai$ */ |