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comparison libtommath/bn_mp_prime_is_prime.c @ 284:eed26cff980b

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propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583) to branch 'au.asn.ucc.matt.dropbear' (head fff0894a0399405a9410ea1c6d118f342cf2aa64)
author Matt Johnston <matt@ucc.asn.au>
date Wed, 08 Mar 2006 13:23:49 +0000
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children 5ff8218bcee9
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283:bd240aa12ba7 284:eed26cff980b
1 #include <tommath.h>
2 #ifdef BN_MP_PRIME_IS_PRIME_C
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
4 *
5 * LibTomMath is a library that provides multiple-precision
6 * integer arithmetic as well as number theoretic functionality.
7 *
8 * The library was designed directly after the MPI library by
9 * Michael Fromberger but has been written from scratch with
10 * additional optimizations in place.
11 *
12 * The library is free for all purposes without any express
13 * guarantee it works.
14 *
15 * Tom St Denis, [email protected], http://math.libtomcrypt.org
16 */
17
18 /* performs a variable number of rounds of Miller-Rabin
19 *
20 * Probability of error after t rounds is no more than
21
22 *
23 * Sets result to 1 if probably prime, 0 otherwise
24 */
25 int mp_prime_is_prime (mp_int * a, int t, int *result)
26 {
27 mp_int b;
28 int ix, err, res;
29
30 /* default to no */
31 *result = MP_NO;
32
33 /* valid value of t? */
34 if (t <= 0 || t > PRIME_SIZE) {
35 return MP_VAL;
36 }
37
38 /* is the input equal to one of the primes in the table? */
39 for (ix = 0; ix < PRIME_SIZE; ix++) {
40 if (mp_cmp_d(a, ltm_prime_tab[ix]) == MP_EQ) {
41 *result = 1;
42 return MP_OKAY;
43 }
44 }
45
46 /* first perform trial division */
47 if ((err = mp_prime_is_divisible (a, &res)) != MP_OKAY) {
48 return err;
49 }
50
51 /* return if it was trivially divisible */
52 if (res == MP_YES) {
53 return MP_OKAY;
54 }
55
56 /* now perform the miller-rabin rounds */
57 if ((err = mp_init (&b)) != MP_OKAY) {
58 return err;
59 }
60
61 for (ix = 0; ix < t; ix++) {
62 /* set the prime */
63 mp_set (&b, ltm_prime_tab[ix]);
64
65 if ((err = mp_prime_miller_rabin (a, &b, &res)) != MP_OKAY) {
66 goto LBL_B;
67 }
68
69 if (res == MP_NO) {
70 goto LBL_B;
71 }
72 }
73
74 /* passed the test */
75 *result = MP_YES;
76 LBL_B:mp_clear (&b);
77 return err;
78 }
79 #endif