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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: prim.c,v 1.2 2000/07/29 09:57:42 mdw Exp $ |
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4 | * |
5 | * Finding primitive elements |
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: prim.c,v $ |
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33 | * Revision 1.2 2000/07/29 09:57:42 mdw |
34 | * Improve primitive-element testing a lot. Now much more sensible and |
35 | * orthogonal: you can find a generator for any given subgroup order by |
36 | * putting in the appropriate parameters. |
37 | * |
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38 | * Revision 1.1 1999/12/22 15:58:59 mdw |
39 | * Search for primitive elements using prime-search equipment. |
40 | * |
41 | */ |
42 | |
43 | /*----- Header files ------------------------------------------------------*/ |
44 | |
45 | #include "mp.h" |
46 | #include "mpint.h" |
47 | #include "mpmont.h" |
48 | #include "mprand.h" |
49 | #include "pgen.h" |
50 | #include "prim.h" |
51 | |
52 | /*----- Main code ---------------------------------------------------------*/ |
53 | |
54 | /* --- @prim_test@ --- */ |
55 | |
56 | int prim_test(int rq, pgen_event *ev, void *p) |
57 | { |
58 | prim_ctx *c = p; |
59 | int rc = rq; |
60 | |
61 | switch (rq) { |
62 | case PGEN_BEGIN: |
63 | return (PGEN_TRY); |
64 | case PGEN_TRY: { |
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65 | mp *x; |
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66 | rc = PGEN_FAIL; |
67 | |
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68 | if (!c->exp) |
69 | x = mp_copy(ev->m); |
70 | else { |
71 | x = mpmont_exp(&c->mm, MP_NEW, ev->m, c->exp); |
72 | if (MP_CMP(x, ==, MP_ONE)) |
73 | goto done; |
74 | } |
75 | if (c->n == 0) |
76 | goto ok; |
77 | else { |
78 | size_t n = c->n; |
79 | mp **f = c->f; |
80 | mp *y = MP_NEW; |
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81 | while (n) { |
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82 | y = mpmont_exp(&c->mm, y, x, *f); |
83 | if (MP_CMP(y, ==, MP_ONE)) { |
84 | mp_drop(y); |
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85 | goto done; |
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86 | } |
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87 | n--; f++; |
88 | } |
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89 | mp_drop(y); |
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90 | } |
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91 | ok: |
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92 | rc = PGEN_DONE; |
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93 | mp_drop(ev->m); |
94 | ev->m = x; |
95 | break; |
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96 | done: |
97 | mp_drop(x); |
98 | } break; |
99 | } |
100 | |
101 | return (rc); |
102 | } |
103 | |
104 | /* --- Trivial stepping functions -----------------------------------------*/ |
105 | |
106 | /* --- @prim_step@ --- */ |
107 | |
108 | int prim_step(int rq, pgen_event *ev, void *p) |
109 | { |
110 | unsigned *i = p; |
111 | switch (rq) { |
112 | case PGEN_BEGIN: |
113 | case PGEN_TRY: |
114 | if (*i >= NPRIME) |
115 | return PGEN_FAIL; |
116 | ev->m = mp_fromint(ev->m, primetab[(*i)++]); |
117 | return (PGEN_TRY); |
118 | } |
119 | return (0); |
120 | } |
121 | |
122 | /*----- That's all, folks -------------------------------------------------*/ |