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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: g-prime.c,v 1.2 2004/04/03 03:32:05 mdw Exp $ |
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4 | * |
5 | * Abstraction for prime groups |
6 | * |
7 | * (c) 2004 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: g-prime.c,v $ |
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33 | * Revision 1.2 2004/04/03 03:32:05 mdw |
34 | * General robustification. |
35 | * |
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36 | * Revision 1.1 2004/04/01 12:50:09 mdw |
37 | * Add cyclic group abstraction, with test code. Separate off exponentation |
38 | * functions for better static linking. Fix a buttload of bugs on the way. |
39 | * Generally ensure that negative exponents do inversion correctly. Add |
40 | * table of standard prime-field subgroups. (Binary field subgroups are |
41 | * currently unimplemented but easy to add if anyone ever finds a good one.) |
42 | * |
43 | */ |
44 | |
45 | /*----- Header files ------------------------------------------------------*/ |
46 | |
47 | #include <mLib/sub.h> |
48 | |
49 | #include "mpmont.h" |
50 | #include "pgen.h" |
51 | |
52 | #define ge mp * |
53 | #include "group.h" |
54 | |
55 | /*----- Data structures ---------------------------------------------------*/ |
56 | |
57 | typedef struct gctx { |
58 | group g; |
59 | mp *gen; |
60 | mpmont mm; |
61 | } gctx; |
62 | |
63 | /*----- Main code ---------------------------------------------------------*/ |
64 | |
65 | /* --- Group operations --- */ |
66 | |
67 | static void gdestroygroup(group *gg) { |
68 | gctx *g = (gctx *)gg; |
69 | mp_drop(g->gen); mp_drop(g->g.r); mp_drop(g->g.h); |
70 | mpmont_destroy(&g->mm); |
71 | DESTROY(g); |
72 | } |
73 | |
74 | static mp **gcreate(group *gg) |
75 | { mp **x = CREATE(mp *); *x = MP_COPY(*gg->i); return (x); } |
76 | |
77 | static void gcopy(group *gg, mp **d, mp **x) |
78 | { mp *t = MP_COPY(*x); MP_DROP(*d); *d = t; } |
79 | |
80 | static void gburn(group *gg, mp **x) { (*x)->f |= MP_BURN; } |
81 | |
82 | static void gdestroy(group *gg, mp **x) { MP_DROP(*x); DESTROY(x); } |
83 | |
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84 | static int gsamep(group *gg, group *hh) { |
85 | gctx *g = (gctx *)gg, *h = (gctx *)hh; |
86 | return (MP_EQ(g->mm.m, h->mm.m)); |
87 | } |
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88 | |
89 | static int geq(group *gg, mp **x, mp **y) { return (MP_EQ(*x, *y)); } |
90 | |
91 | static const char *gcheck(group *gg, grand *gr) { |
92 | gctx *g = (gctx *)gg; int rc; mp *t; |
93 | if (!pgen_primep(g->mm.m, gr)) return ("p is not prime"); |
94 | t = mp_mul(MP_NEW, g->g.r, g->g.h); t = mp_add(t, t, MP_ONE); |
95 | rc = MP_EQ(t, g->mm.m); MP_DROP(t); if (!rc) return ("not a subgroup"); |
96 | return (group_stdcheck(gg, gr)); |
97 | } |
98 | |
99 | static void gmul(group *gg, mp **d, mp **x, mp **y) |
100 | { gctx *g = (gctx *)gg; *d = mpmont_mul(&g->mm, *d, *x, *y); } |
101 | |
102 | static void gsqr(group *gg, mp **d, mp **x) { |
103 | gctx *g = (gctx *)gg; mp *r = mp_sqr(*d, *x); |
104 | *d = mpmont_reduce(&g->mm, r, r); |
105 | } |
106 | |
107 | static void ginv(group *gg, mp **d, mp **x) { |
108 | gctx *g = (gctx *)gg; mp *r = mpmont_reduce(&g->mm, *d, *x); |
109 | mp_gcd(0, 0, &r, g->mm.m, r); *d = mpmont_mul(&g->mm, r, r, g->mm.r2); |
110 | } |
111 | |
112 | static void gexp(group *gg, mp **d, mp **x, mp *n) |
113 | { gctx *g = (gctx *)gg; *d = mpmont_expr(&g->mm, *d, *x, n); } |
114 | |
115 | static void gmexp(group *gg, mp **d, const group_expfactor *f, size_t n) { |
116 | gctx *g = (gctx *)gg; size_t i; |
117 | mp_expfactor *ff = xmalloc(n * sizeof(mp_expfactor)); |
118 | for (i = 0; i < n; i++) { ff[i].base = *f[i].base; ff[i].exp = f[i].exp; } |
119 | *d = mpmont_mexpr(&g->mm, *d, ff, n); xfree(ff); |
120 | } |
121 | |
122 | static int gread(group *gg, mp **d, const mptext_ops *ops, void *p) { |
123 | gctx *g = (gctx *)gg; mp *t; |
124 | if ((t = mp_read(MP_NEW, 0, ops, p)) == 0) return (-1); |
125 | mp_drop(*d); *d = mpmont_mul(&g->mm, t, t, g->mm.r2); return (0); |
126 | } |
127 | |
128 | static int gwrite(group *gg, mp **x, const mptext_ops *ops, void *p) { |
129 | gctx *g = (gctx *)gg; mp *t = mpmont_reduce(&g->mm, MP_NEW, *x); |
130 | int rc = mp_write(t, 10, ops, p); MP_DROP(t); return (rc); |
131 | } |
132 | |
133 | static mp *gtoint(group *gg, mp *d, mp **x) |
134 | { gctx *g = (gctx *)gg; return (mpmont_reduce(&g->mm, d, *x)); } |
135 | |
136 | static int gfromint(group *gg, mp **d, mp *x) { |
137 | gctx *g = (gctx *)gg; mp_div(0, &x, x, g->mm.m); mp_drop(*d); |
138 | *d = mpmont_mul(&g->mm, x, x, g->mm.r2); return (0); |
139 | } |
140 | |
141 | static int gtobuf(group *gg, buf *b, mp **x) { |
142 | gctx *g = (gctx *)gg; mp *t = mpmont_reduce(&g->mm, MP_NEW, *x); |
143 | int rc = buf_putmp(b, t); MP_DROP(t); return (rc); |
144 | } |
145 | |
146 | static int gfrombuf(group *gg, buf *b, mp **d) { |
147 | gctx * g = (gctx *)gg; mp *x; if ((x = buf_getmp(b)) == 0) return (-1); |
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148 | mp_div(0, &x, x, g->mm.m); mp_drop(*d); |
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149 | *d = mpmont_mul(&g->mm, x, x, g->mm.r2); return(0); |
150 | } |
151 | |
152 | /* --- @group_prime@ --- * |
153 | * |
154 | * Arguments: @const gprime_param *gp@ = group parameters |
155 | * |
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156 | * Returns: A pointer to the group, or null. |
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157 | * |
158 | * Use: Constructs an abstract group interface for a subgroup of a |
159 | * prime field. Group elements are @mp *@ pointers. |
160 | */ |
161 | |
162 | static const group_ops gops = { |
163 | GTY_PRIME, |
164 | gdestroygroup, gcreate, gcopy, gburn, gdestroy, |
165 | gsamep, geq, group_stdidentp, |
166 | gcheck, |
167 | gmul, gsqr, ginv, group_stddiv, gexp, gmexp, |
168 | gread, gwrite, |
169 | gtoint, gfromint, group_stdtoec, group_stdfromec, gtobuf, gfrombuf |
170 | }; |
171 | |
172 | group *group_prime(const gprime_param *gp) |
173 | { |
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174 | gctx *g; |
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175 | |
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176 | if (!MP_ISPOS(gp->p) || !MP_ISODD(gp->p)) |
177 | return (0); |
178 | g = CREATE(gctx); |
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179 | g->g.ops = &gops; |
180 | g->g.nbits = mp_bits(gp->p); |
181 | g->g.noctets = (g->g.nbits + 7) >> 3; |
182 | mpmont_create(&g->mm, gp->p); |
183 | g->g.i = &g->mm.r; |
184 | g->gen = mpmont_mul(&g->mm, MP_NEW, gp->g, g->mm.r2); |
185 | g->g.g = &g->gen; |
186 | g->g.r = MP_COPY(gp->q); |
187 | g->g.h = MP_NEW; mp_div(&g->g.h, 0, gp->p, gp->q); |
188 | return (&g->g); |
189 | } |
190 | |
191 | /*----- That's all, folks -------------------------------------------------*/ |