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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: pgen-safe.c,v 1.2 2000/02/12 18:21:03 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 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: pgen-safe.c,v $ |
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33 | * Revision 1.2 2000/02/12 18:21:03 mdw |
34 | * Overhaul of key management (again). |
35 | * |
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36 | * Revision 1.1 1999/12/22 16:01:34 mdw |
37 | * Find `safe' primes (i.e., %$p = 2q + 1$%). |
38 | * |
39 | */ |
40 | |
41 | /*----- Header files ------------------------------------------------------*/ |
42 | |
43 | #include "mp.h" |
44 | #include "mprand.h" |
45 | #include "pgen.h" |
46 | |
47 | /*----- Main code ---------------------------------------------------------*/ |
48 | |
49 | /* --- @pgen_safestep@ --- * |
50 | * |
51 | * Steps two numbers, %$q$% and %$p = 2q + 1$%, such that neither has any |
52 | * small factors. %$p$% is put in the event block. |
53 | */ |
54 | |
55 | int pgen_safestep(int rq, pgen_event *ev, void *p) |
56 | { |
57 | pgen_safestepctx *c = p; |
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58 | int rc = PGEN_ABORT, qrc = 0; |
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59 | |
60 | switch (rq) { |
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61 | |
62 | /* --- Set up the contexts --- */ |
63 | |
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64 | case PGEN_BEGIN: { |
65 | mp *p = mp_split(MP_COPY(ev->m)); |
66 | mp *q; |
67 | p->v[0] |= 3; |
68 | q = mp_lsr(MP_NEW, p, 1); |
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69 | rc = pfilt_create(&c->p, p); |
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70 | qrc = pfilt_create(&c->q, q); |
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71 | mp_drop(p); mp_drop(q); |
72 | } break; |
73 | |
74 | /* --- Step along --- */ |
75 | |
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76 | case PGEN_TRY: |
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77 | mp_drop(ev->m); |
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78 | rc = pfilt_step(&c->p, 4); |
79 | qrc = pfilt_step(&c->q, 2); |
80 | break; |
81 | |
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82 | break; |
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83 | |
84 | /* --- Tidy the toys away --- */ |
85 | |
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86 | case PGEN_DONE: |
87 | pfilt_destroy(&c->q); |
88 | pfilt_destroy(&c->p); |
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89 | return (PGEN_DONE); |
90 | } |
91 | |
92 | /* --- Continue stepping if necessary --- */ |
93 | |
94 | while (rc == PGEN_FAIL || qrc == PGEN_FAIL) { |
95 | rc = pfilt_step(&c->p, 4); |
96 | qrc = pfilt_step(&c->q, 2); |
97 | } |
98 | |
99 | ev->m = MP_COPY(c->p.m); |
100 | if (qrc == PGEN_TRY) |
101 | rc = PGEN_TRY; |
102 | return (rc); |
103 | } |
104 | |
105 | /* --- @pgen_safejump@ --- * |
106 | * |
107 | * Jumps two numbers, %$q$% and %$p = 2q + 1$% such that neither has any |
108 | * small factors. |
109 | */ |
110 | |
111 | int pgen_safejump(int rq, pgen_event *ev, void *p) |
112 | { |
113 | pgen_safejumpctx *j = p; |
114 | int rc = PGEN_ABORT, qrc = 0; |
115 | |
116 | switch (rq) { |
117 | |
118 | /* --- Set up the jump contexts --- * |
119 | * |
120 | * The jump in @j.q@ is congruent to 2 (mod 4); see @strongprime_setup@. |
121 | * If @p@ is initially 1 (mod 4) then add @j.q@. Then double @j.q@ to |
122 | * ensure that the step is 0 (mod 4). |
123 | */ |
124 | |
125 | case PGEN_BEGIN: { |
126 | mp *p = ev->m; |
127 | mp *q; |
128 | if ((p->v[0] & 3) != 3) |
129 | p = mp_add(p, p, j->jq.m); |
130 | rc = pfilt_create(&j->p, p); |
131 | pfilt_muladd(&j->jp, &j->jq, 2, 0); |
132 | q = mp_lsr(MP_NEW, p, 1); |
133 | qrc = pfilt_create(&j->q, q); |
134 | mp_drop(p); |
135 | mp_drop(q); |
136 | } break; |
137 | |
138 | /* --- Step on one place --- */ |
139 | |
140 | case PGEN_TRY: |
141 | mp_drop(ev->m); |
142 | rc = pfilt_jump(&j->p, &j->jp); |
143 | qrc = pfilt_jump(&j->q, &j->jq); |
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144 | break; |
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145 | |
146 | /* --- Tidy everything up --- */ |
147 | |
148 | case PGEN_DONE: |
149 | pfilt_destroy(&j->jp); |
150 | pfilt_destroy(&j->p); |
151 | pfilt_destroy(&j->q); |
152 | return (PGEN_DONE); |
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153 | } |
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154 | |
155 | /* --- Step on while @p@ or @q@ have small factors --- */ |
156 | |
157 | while (rc == PGEN_FAIL || qrc == PGEN_FAIL) { |
158 | rc = pfilt_jump(&j->p, &j->jp); |
159 | qrc = pfilt_jump(&j->q, &j->jq); |
160 | } |
161 | ev->m = MP_COPY(j->p.m); |
162 | if (qrc == PGEN_TRY) |
163 | rc = PGEN_TRY; |
164 | return (rc); |
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165 | } |
166 | |
167 | /* --- @pgen_safetest@ --- * |
168 | * |
169 | * Applies Rabin-Miller tests to %$p$% and %$q$%. |
170 | */ |
171 | |
172 | int pgen_safetest(int rq, pgen_event *ev, void *p) |
173 | { |
174 | pgen_safetestctx *c = p; |
175 | int rc = PGEN_ABORT; |
176 | |
177 | switch (rq) { |
178 | case PGEN_BEGIN: |
179 | rabin_create(&c->q, c->c.q.m); |
180 | rabin_create(&c->p, c->c.p.m); |
181 | rc = PGEN_TRY; |
182 | break; |
183 | case PGEN_TRY: { |
184 | mp *m = mprand_range(MP_NEW, c->c.q.m, ev->r, 0); |
185 | rc = rabin_test(&c->p, m); |
186 | if (rc == PGEN_PASS) |
187 | rc = rabin_test(&c->q, m); |
188 | mp_drop(m); |
189 | } break; |
190 | case PGEN_DONE: |
191 | rabin_destroy(&c->q); |
192 | rabin_destroy(&c->p); |
193 | break; |
194 | } |
195 | return (rc); |
196 | } |
197 | |
198 | /*----- That's all, folks -------------------------------------------------*/ |