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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: pgen-safe.c,v 1.5 2004/04/08 01:36:15 mdw Exp $ |
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4 | * |
5 | * Safe prime generation |
6 | * |
7 | * (c) 1999 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of Catacomb. |
13 | * |
14 | * Catacomb is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the |
17 | * License, or (at your option) any later version. |
18 | * |
19 | * Catacomb is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU Library General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with Catacomb; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
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30 | /*----- Header files ------------------------------------------------------*/ |
31 | |
32 | #include "mp.h" |
33 | #include "mprand.h" |
34 | #include "pgen.h" |
35 | |
36 | /*----- Main code ---------------------------------------------------------*/ |
37 | |
38 | /* --- @pgen_safestep@ --- * |
39 | * |
40 | * Steps two numbers, %$q$% and %$p = 2q + 1$%, such that neither has any |
41 | * small factors. %$p$% is put in the event block. |
42 | */ |
43 | |
44 | int pgen_safestep(int rq, pgen_event *ev, void *p) |
45 | { |
46 | pgen_safestepctx *c = p; |
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47 | int rc = PGEN_ABORT, qrc = 0; |
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48 | |
49 | switch (rq) { |
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50 | |
51 | /* --- Set up the contexts --- */ |
52 | |
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53 | case PGEN_BEGIN: { |
54 | mp *p = mp_split(MP_COPY(ev->m)); |
55 | mp *q; |
56 | p->v[0] |= 3; |
57 | q = mp_lsr(MP_NEW, p, 1); |
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58 | rc = pfilt_create(&c->p, p); |
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59 | qrc = pfilt_create(&c->q, q); |
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60 | mp_drop(p); mp_drop(q); |
61 | } break; |
62 | |
63 | /* --- Step along --- */ |
64 | |
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65 | case PGEN_TRY: |
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66 | mp_drop(ev->m); |
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67 | rc = pfilt_step(&c->p, 4); |
68 | qrc = pfilt_step(&c->q, 2); |
69 | break; |
70 | |
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71 | break; |
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72 | |
73 | /* --- Tidy the toys away --- */ |
74 | |
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75 | case PGEN_DONE: |
76 | pfilt_destroy(&c->q); |
77 | pfilt_destroy(&c->p); |
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78 | return (PGEN_DONE); |
79 | } |
80 | |
81 | /* --- Continue stepping if necessary --- */ |
82 | |
83 | while (rc == PGEN_FAIL || qrc == PGEN_FAIL) { |
84 | rc = pfilt_step(&c->p, 4); |
85 | qrc = pfilt_step(&c->q, 2); |
86 | } |
87 | |
88 | ev->m = MP_COPY(c->p.m); |
89 | if (qrc == PGEN_TRY) |
90 | rc = PGEN_TRY; |
91 | return (rc); |
92 | } |
93 | |
94 | /* --- @pgen_safejump@ --- * |
95 | * |
96 | * Jumps two numbers, %$q$% and %$p = 2q + 1$% such that neither has any |
97 | * small factors. |
98 | */ |
99 | |
100 | int pgen_safejump(int rq, pgen_event *ev, void *p) |
101 | { |
102 | pgen_safejumpctx *j = p; |
103 | int rc = PGEN_ABORT, qrc = 0; |
104 | |
105 | switch (rq) { |
106 | |
107 | /* --- Set up the jump contexts --- * |
108 | * |
109 | * The jump in @j.q@ is congruent to 2 (mod 4); see @strongprime_setup@. |
110 | * If @p@ is initially 1 (mod 4) then add @j.q@. Then double @j.q@ to |
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111 | * ensure that the step is 0 (mod 4). Ensure that @jq@ and @q@ don't |
112 | * have any common factors. |
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113 | */ |
114 | |
115 | case PGEN_BEGIN: { |
116 | mp *p = ev->m; |
117 | mp *q; |
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118 | mp *g = MP_NEW; |
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119 | if ((p->v[0] & 3) != 3) |
120 | p = mp_add(p, p, j->jq.m); |
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121 | q = mp_lsr(MP_NEW, p, 1); |
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122 | mp_gcd(&g, 0, 0, p, j->jq.m); |
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123 | if (MP_CMP(g, >, MP_ONE)) { |
124 | ev->m = p; |
125 | mp_drop(q); |
126 | mp_drop(g); |
127 | return (PGEN_ABORT); |
128 | } |
129 | mp_drop(g); |
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130 | rc = pfilt_create(&j->p, p); |
131 | pfilt_muladd(&j->jp, &j->jq, 2, 0); |
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132 | qrc = pfilt_create(&j->q, q); |
133 | mp_drop(p); |
134 | mp_drop(q); |
135 | } break; |
136 | |
137 | /* --- Step on one place --- */ |
138 | |
139 | case PGEN_TRY: |
140 | mp_drop(ev->m); |
141 | rc = pfilt_jump(&j->p, &j->jp); |
142 | qrc = pfilt_jump(&j->q, &j->jq); |
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143 | break; |
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144 | |
145 | /* --- Tidy everything up --- */ |
146 | |
147 | case PGEN_DONE: |
148 | pfilt_destroy(&j->jp); |
149 | pfilt_destroy(&j->p); |
150 | pfilt_destroy(&j->q); |
151 | return (PGEN_DONE); |
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152 | } |
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153 | |
154 | /* --- Step on while @p@ or @q@ have small factors --- */ |
155 | |
156 | while (rc == PGEN_FAIL || qrc == PGEN_FAIL) { |
157 | rc = pfilt_jump(&j->p, &j->jp); |
158 | qrc = pfilt_jump(&j->q, &j->jq); |
159 | } |
160 | ev->m = MP_COPY(j->p.m); |
161 | if (qrc == PGEN_TRY) |
162 | rc = PGEN_TRY; |
163 | return (rc); |
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164 | } |
165 | |
166 | /* --- @pgen_safetest@ --- * |
167 | * |
168 | * Applies Rabin-Miller tests to %$p$% and %$q$%. |
169 | */ |
170 | |
171 | int pgen_safetest(int rq, pgen_event *ev, void *p) |
172 | { |
173 | pgen_safetestctx *c = p; |
174 | int rc = PGEN_ABORT; |
175 | |
176 | switch (rq) { |
177 | case PGEN_BEGIN: |
178 | rabin_create(&c->q, c->c.q.m); |
179 | rabin_create(&c->p, c->c.p.m); |
180 | rc = PGEN_TRY; |
181 | break; |
182 | case PGEN_TRY: { |
183 | mp *m = mprand_range(MP_NEW, c->c.q.m, ev->r, 0); |
184 | rc = rabin_test(&c->p, m); |
185 | if (rc == PGEN_PASS) |
186 | rc = rabin_test(&c->q, m); |
187 | mp_drop(m); |
188 | } break; |
189 | case PGEN_DONE: |
190 | rabin_destroy(&c->q); |
191 | rabin_destroy(&c->p); |
192 | break; |
193 | } |
194 | return (rc); |
195 | } |
196 | |
197 | /*----- That's all, folks -------------------------------------------------*/ |