Mercurial > dropbear

annotate libtommath/bn_mp_prime_is_prime.c @ 368:ed910547d449

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Free x component of DSS key upon failure to load (found by Klocwork)
author Matt Johnston <matt@ucc.asn.au>
date Thu, 02 Nov 2006 14:49:20 +0000
parents eed26cff980b
children 5ff8218bcee9
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284
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diff changeset
1 #include <tommath.h>
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2 #ifdef BN_MP_PRIME_IS_PRIME_C
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3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
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4 *
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5 * LibTomMath is a library that provides multiple-precision
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6 * integer arithmetic as well as number theoretic functionality.
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7 *
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8 * The library was designed directly after the MPI library by
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9 * Michael Fromberger but has been written from scratch with
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10 * additional optimizations in place.
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11 *
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12 * The library is free for all purposes without any express
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13 * guarantee it works.
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14 *
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15 * Tom St Denis, [email protected], http://math.libtomcrypt.org
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16 */
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17
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18 /* performs a variable number of rounds of Miller-Rabin
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19 *
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20 * Probability of error after t rounds is no more than
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21
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22 *
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23 * Sets result to 1 if probably prime, 0 otherwise
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24 */
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25 int mp_prime_is_prime (mp_int * a, int t, int *result)
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26 {
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27 mp_int b;
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28 int ix, err, res;
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29
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30 /* default to no */
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31 *result = MP_NO;
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32
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33 /* valid value of t? */
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34 if (t <= 0 || t > PRIME_SIZE) {
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35 return MP_VAL;
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36 }
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37
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38 /* is the input equal to one of the primes in the table? */
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39 for (ix = 0; ix < PRIME_SIZE; ix++) {
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40 if (mp_cmp_d(a, ltm_prime_tab[ix]) == MP_EQ) {
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41 *result = 1;
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42 return MP_OKAY;
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43 }
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44 }
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45
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46 /* first perform trial division */
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47 if ((err = mp_prime_is_divisible (a, &res)) != MP_OKAY) {
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48 return err;
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49 }
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50
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51 /* return if it was trivially divisible */
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52 if (res == MP_YES) {
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53 return MP_OKAY;
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54 }
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55
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56 /* now perform the miller-rabin rounds */
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57 if ((err = mp_init (&b)) != MP_OKAY) {
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58 return err;
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59 }
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60
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61 for (ix = 0; ix < t; ix++) {
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62 /* set the prime */
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63 mp_set (&b, ltm_prime_tab[ix]);
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64
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65 if ((err = mp_prime_miller_rabin (a, &b, &res)) != MP_OKAY) {
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66 goto LBL_B;
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67 }
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68
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69 if (res == MP_NO) {
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70 goto LBL_B;
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71 }
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72 }
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73
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74 /* passed the test */
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75 *result = MP_YES;
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76 LBL_B:mp_clear (&b);
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77 return err;
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78 }
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79 #endif