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comparison bn_mp_prime_miller_rabin.c @ 190:d8254fc979e9 libtommath-orig LTM_0.35

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Initial import of libtommath 0.35
author Matt Johnston <matt@ucc.asn.au>
date Fri, 06 May 2005 08:59:30 +0000
parents d29b64170cf0
children
comparison
equal deleted inserted replaced
142:d29b64170cf0 190:d8254fc979e9
38 /* get n1 = a - 1 */ 38 /* get n1 = a - 1 */
39 if ((err = mp_init_copy (&n1, a)) != MP_OKAY) { 39 if ((err = mp_init_copy (&n1, a)) != MP_OKAY) {
40 return err; 40 return err;
41 } 41 }
42 if ((err = mp_sub_d (&n1, 1, &n1)) != MP_OKAY) { 42 if ((err = mp_sub_d (&n1, 1, &n1)) != MP_OKAY) {
43 goto __N1; 43 goto LBL_N1;
44 } 44 }
45 45
46 /* set 2**s * r = n1 */ 46 /* set 2**s * r = n1 */
47 if ((err = mp_init_copy (&r, &n1)) != MP_OKAY) { 47 if ((err = mp_init_copy (&r, &n1)) != MP_OKAY) {
48 goto __N1; 48 goto LBL_N1;
49 } 49 }
50 50
51 /* count the number of least significant bits 51 /* count the number of least significant bits
52 * which are zero 52 * which are zero
53 */ 53 */
54 s = mp_cnt_lsb(&r); 54 s = mp_cnt_lsb(&r);
55 55
56 /* now divide n - 1 by 2**s */ 56 /* now divide n - 1 by 2**s */
57 if ((err = mp_div_2d (&r, s, &r, NULL)) != MP_OKAY) { 57 if ((err = mp_div_2d (&r, s, &r, NULL)) != MP_OKAY) {
58 goto __R; 58 goto LBL_R;
59 } 59 }
60 60
61 /* compute y = b**r mod a */ 61 /* compute y = b**r mod a */
62 if ((err = mp_init (&y)) != MP_OKAY) { 62 if ((err = mp_init (&y)) != MP_OKAY) {
63 goto __R; 63 goto LBL_R;
64 } 64 }
65 if ((err = mp_exptmod (b, &r, a, &y)) != MP_OKAY) { 65 if ((err = mp_exptmod (b, &r, a, &y)) != MP_OKAY) {
66 goto __Y; 66 goto LBL_Y;
67 } 67 }
68 68
69 /* if y != 1 and y != n1 do */ 69 /* if y != 1 and y != n1 do */
70 if (mp_cmp_d (&y, 1) != MP_EQ && mp_cmp (&y, &n1) != MP_EQ) { 70 if (mp_cmp_d (&y, 1) != MP_EQ && mp_cmp (&y, &n1) != MP_EQ) {
71 j = 1; 71 j = 1;
72 /* while j <= s-1 and y != n1 */ 72 /* while j <= s-1 and y != n1 */
73 while ((j <= (s - 1)) && mp_cmp (&y, &n1) != MP_EQ) { 73 while ((j <= (s - 1)) && mp_cmp (&y, &n1) != MP_EQ) {
74 if ((err = mp_sqrmod (&y, a, &y)) != MP_OKAY) { 74 if ((err = mp_sqrmod (&y, a, &y)) != MP_OKAY) {
75 goto __Y; 75 goto LBL_Y;
76 } 76 }
77 77
78 /* if y == 1 then composite */ 78 /* if y == 1 then composite */
79 if (mp_cmp_d (&y, 1) == MP_EQ) { 79 if (mp_cmp_d (&y, 1) == MP_EQ) {
80 goto __Y; 80 goto LBL_Y;
81 } 81 }
82 82
83 ++j; 83 ++j;
84 } 84 }
85 85
86 /* if y != n1 then composite */ 86 /* if y != n1 then composite */
87 if (mp_cmp (&y, &n1) != MP_EQ) { 87 if (mp_cmp (&y, &n1) != MP_EQ) {
88 goto __Y; 88 goto LBL_Y;
89 } 89 }
90 } 90 }
91 91
92 /* probably prime now */ 92 /* probably prime now */
93 *result = MP_YES; 93 *result = MP_YES;
94 __Y:mp_clear (&y); 94 LBL_Y:mp_clear (&y);
95 __R:mp_clear (&r); 95 LBL_R:mp_clear (&r);
96 __N1:mp_clear (&n1); 96 LBL_N1:mp_clear (&n1);
97 return err; 97 return err;
98 } 98 }
99 #endif 99 #endif