3 * $Id: pgen-safe.c,v 1.3 2000/06/17 11:52:36 mdw Exp $
5 * Safe prime generation
7 * (c) 1999 Straylight/Edgeware
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of Catacomb.
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.
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.
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,
30 /*----- Revision history --------------------------------------------------*
32 * $Log: pgen-safe.c,v $
33 * Revision 1.3 2000/06/17 11:52:36 mdw
34 * Signal a pgen abort if the jump and base share a common factor.
36 * Revision 1.2 2000/02/12 18:21:03 mdw
37 * Overhaul of key management (again).
39 * Revision 1.1 1999/12/22 16:01:34 mdw
40 * Find `safe' primes (i.e., %$p = 2q + 1$%).
44 /*----- Header files ------------------------------------------------------*/
50 /*----- Main code ---------------------------------------------------------*/
52 /* --- @pgen_safestep@ --- *
54 * Steps two numbers, %$q$% and %$p = 2q + 1$%, such that neither has any
55 * small factors. %$p$% is put in the event block.
58 int pgen_safestep(int rq
, pgen_event
*ev
, void *p
)
60 pgen_safestepctx
*c
= p
;
61 int rc
= PGEN_ABORT
, qrc
= 0;
65 /* --- Set up the contexts --- */
68 mp
*p
= mp_split(MP_COPY(ev
->m
));
71 q
= mp_lsr(MP_NEW
, p
, 1);
72 rc
= pfilt_create(&c
->p
, p
);
73 qrc
= pfilt_create(&c
->q
, q
);
74 mp_drop(p
); mp_drop(q
);
77 /* --- Step along --- */
81 rc
= pfilt_step(&c
->p
, 4);
82 qrc
= pfilt_step(&c
->q
, 2);
87 /* --- Tidy the toys away --- */
95 /* --- Continue stepping if necessary --- */
97 while (rc
== PGEN_FAIL
|| qrc
== PGEN_FAIL
) {
98 rc
= pfilt_step(&c
->p
, 4);
99 qrc
= pfilt_step(&c
->q
, 2);
102 ev
->m
= MP_COPY(c
->p
.m
);
108 /* --- @pgen_safejump@ --- *
110 * Jumps two numbers, %$q$% and %$p = 2q + 1$% such that neither has any
114 int pgen_safejump(int rq
, pgen_event
*ev
, void *p
)
116 pgen_safejumpctx
*j
= p
;
117 int rc
= PGEN_ABORT
, qrc
= 0;
121 /* --- Set up the jump contexts --- *
123 * The jump in @j.q@ is congruent to 2 (mod 4); see @strongprime_setup@.
124 * If @p@ is initially 1 (mod 4) then add @j.q@. Then double @j.q@ to
125 * ensure that the step is 0 (mod 4). Ensure that @jq@ and @q@ don't
126 * have any common factors.
133 if ((p
->v
[0] & 3) != 3)
134 p
= mp_add(p
, p
, j
->jq
.m
);
135 q
= mp_lsr(MP_NEW
, p
, 1);
136 mp_gcd(&g
, 0, 0, q
, j
->jq
.m
);
137 if (MP_CMP(g
, >, MP_ONE
)) {
144 rc
= pfilt_create(&j
->p
, p
);
145 pfilt_muladd(&j
->jp
, &j
->jq
, 2, 0);
146 qrc
= pfilt_create(&j
->q
, q
);
151 /* --- Step on one place --- */
155 rc
= pfilt_jump(&j
->p
, &j
->jp
);
156 qrc
= pfilt_jump(&j
->q
, &j
->jq
);
159 /* --- Tidy everything up --- */
162 pfilt_destroy(&j
->jp
);
163 pfilt_destroy(&j
->p
);
164 pfilt_destroy(&j
->q
);
168 /* --- Step on while @p@ or @q@ have small factors --- */
170 while (rc
== PGEN_FAIL
|| qrc
== PGEN_FAIL
) {
171 rc
= pfilt_jump(&j
->p
, &j
->jp
);
172 qrc
= pfilt_jump(&j
->q
, &j
->jq
);
174 ev
->m
= MP_COPY(j
->p
.m
);
180 /* --- @pgen_safetest@ --- *
182 * Applies Rabin-Miller tests to %$p$% and %$q$%.
185 int pgen_safetest(int rq
, pgen_event
*ev
, void *p
)
187 pgen_safetestctx
*c
= p
;
192 rabin_create(&c
->q
, c
->c
.q
.m
);
193 rabin_create(&c
->p
, c
->c
.p
.m
);
197 mp
*m
= mprand_range(MP_NEW
, c
->c
.q
.m
, ev
->r
, 0);
198 rc
= rabin_test(&c
->p
, m
);
200 rc
= rabin_test(&c
->q
, m
);
204 rabin_destroy(&c
->q
);
205 rabin_destroy(&c
->p
);
211 /*----- That's all, folks -------------------------------------------------*/