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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: g-prime.c,v 1.3 2004/04/04 19:04:11 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 1.3 2004/04/04 19:04:11 mdw |
34 | * Raw I/O of elliptic curve points and group elements. |
35 | * |
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36 | * Revision 1.2 2004/04/03 03:32:05 mdw |
37 | * General robustification. |
38 | * |
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39 | * Revision 1.1 2004/04/01 12:50:09 mdw |
40 | * Add cyclic group abstraction, with test code. Separate off exponentation |
41 | * functions for better static linking. Fix a buttload of bugs on the way. |
42 | * Generally ensure that negative exponents do inversion correctly. Add |
43 | * table of standard prime-field subgroups. (Binary field subgroups are |
44 | * currently unimplemented but easy to add if anyone ever finds a good one.) |
45 | * |
46 | */ |
47 | |
48 | /*----- Header files ------------------------------------------------------*/ |
49 | |
50 | #include <mLib/sub.h> |
51 | |
52 | #include "mpmont.h" |
53 | #include "pgen.h" |
54 | |
55 | #define ge mp * |
56 | #include "group.h" |
57 | |
58 | /*----- Data structures ---------------------------------------------------*/ |
59 | |
60 | typedef struct gctx { |
61 | group g; |
62 | mp *gen; |
63 | mpmont mm; |
64 | } gctx; |
65 | |
66 | /*----- Main code ---------------------------------------------------------*/ |
67 | |
68 | /* --- Group operations --- */ |
69 | |
70 | static void gdestroygroup(group *gg) { |
71 | gctx *g = (gctx *)gg; |
72 | mp_drop(g->gen); mp_drop(g->g.r); mp_drop(g->g.h); |
73 | mpmont_destroy(&g->mm); |
74 | DESTROY(g); |
75 | } |
76 | |
77 | static mp **gcreate(group *gg) |
78 | { mp **x = CREATE(mp *); *x = MP_COPY(*gg->i); return (x); } |
79 | |
80 | static void gcopy(group *gg, mp **d, mp **x) |
81 | { mp *t = MP_COPY(*x); MP_DROP(*d); *d = t; } |
82 | |
83 | static void gburn(group *gg, mp **x) { (*x)->f |= MP_BURN; } |
84 | |
85 | static void gdestroy(group *gg, mp **x) { MP_DROP(*x); DESTROY(x); } |
86 | |
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87 | static int gsamep(group *gg, group *hh) { |
88 | gctx *g = (gctx *)gg, *h = (gctx *)hh; |
89 | return (MP_EQ(g->mm.m, h->mm.m)); |
90 | } |
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91 | |
92 | static int geq(group *gg, mp **x, mp **y) { return (MP_EQ(*x, *y)); } |
93 | |
94 | static const char *gcheck(group *gg, grand *gr) { |
95 | gctx *g = (gctx *)gg; int rc; mp *t; |
96 | if (!pgen_primep(g->mm.m, gr)) return ("p is not prime"); |
97 | t = mp_mul(MP_NEW, g->g.r, g->g.h); t = mp_add(t, t, MP_ONE); |
98 | rc = MP_EQ(t, g->mm.m); MP_DROP(t); if (!rc) return ("not a subgroup"); |
99 | return (group_stdcheck(gg, gr)); |
100 | } |
101 | |
102 | static void gmul(group *gg, mp **d, mp **x, mp **y) |
103 | { gctx *g = (gctx *)gg; *d = mpmont_mul(&g->mm, *d, *x, *y); } |
104 | |
105 | static void gsqr(group *gg, mp **d, mp **x) { |
106 | gctx *g = (gctx *)gg; mp *r = mp_sqr(*d, *x); |
107 | *d = mpmont_reduce(&g->mm, r, r); |
108 | } |
109 | |
110 | static void ginv(group *gg, mp **d, mp **x) { |
111 | gctx *g = (gctx *)gg; mp *r = mpmont_reduce(&g->mm, *d, *x); |
112 | mp_gcd(0, 0, &r, g->mm.m, r); *d = mpmont_mul(&g->mm, r, r, g->mm.r2); |
113 | } |
114 | |
115 | static void gexp(group *gg, mp **d, mp **x, mp *n) |
116 | { gctx *g = (gctx *)gg; *d = mpmont_expr(&g->mm, *d, *x, n); } |
117 | |
118 | static void gmexp(group *gg, mp **d, const group_expfactor *f, size_t n) { |
119 | gctx *g = (gctx *)gg; size_t i; |
120 | mp_expfactor *ff = xmalloc(n * sizeof(mp_expfactor)); |
121 | for (i = 0; i < n; i++) { ff[i].base = *f[i].base; ff[i].exp = f[i].exp; } |
122 | *d = mpmont_mexpr(&g->mm, *d, ff, n); xfree(ff); |
123 | } |
124 | |
125 | static int gread(group *gg, mp **d, const mptext_ops *ops, void *p) { |
126 | gctx *g = (gctx *)gg; mp *t; |
127 | if ((t = mp_read(MP_NEW, 0, ops, p)) == 0) return (-1); |
128 | mp_drop(*d); *d = mpmont_mul(&g->mm, t, t, g->mm.r2); return (0); |
129 | } |
130 | |
131 | static int gwrite(group *gg, mp **x, const mptext_ops *ops, void *p) { |
132 | gctx *g = (gctx *)gg; mp *t = mpmont_reduce(&g->mm, MP_NEW, *x); |
133 | int rc = mp_write(t, 10, ops, p); MP_DROP(t); return (rc); |
134 | } |
135 | |
136 | static mp *gtoint(group *gg, mp *d, mp **x) |
137 | { gctx *g = (gctx *)gg; return (mpmont_reduce(&g->mm, d, *x)); } |
138 | |
139 | static int gfromint(group *gg, mp **d, mp *x) { |
140 | gctx *g = (gctx *)gg; mp_div(0, &x, x, g->mm.m); mp_drop(*d); |
141 | *d = mpmont_mul(&g->mm, x, x, g->mm.r2); return (0); |
142 | } |
143 | |
144 | static int gtobuf(group *gg, buf *b, mp **x) { |
145 | gctx *g = (gctx *)gg; mp *t = mpmont_reduce(&g->mm, MP_NEW, *x); |
146 | int rc = buf_putmp(b, t); MP_DROP(t); return (rc); |
147 | } |
148 | |
149 | static int gfrombuf(group *gg, buf *b, mp **d) { |
150 | gctx * g = (gctx *)gg; mp *x; if ((x = buf_getmp(b)) == 0) return (-1); |
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151 | mp_div(0, &x, x, g->mm.m); mp_drop(*d); |
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152 | *d = mpmont_mul(&g->mm, x, x, g->mm.r2); return(0); |
153 | } |
154 | |
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155 | static int gtoraw(group *gg, buf *b, mp **x) { |
156 | gctx *g = (gctx *)gg; octet *q; mp *t = mpmont_reduce(&g->mm, MP_NEW, *x); |
157 | if ((q = buf_get(b, g->g.noctets)) == 0) { MP_DROP(t); return (-1); } |
158 | mp_storeb(t, q, g->g.noctets); MP_DROP(t); return (0); |
159 | } |
160 | |
161 | static int gfromraw(group *gg, buf *b, mp **d) { |
162 | gctx * g = (gctx *)gg; mp *x; octet *q; |
163 | if ((q = buf_get(b, g->g.noctets)) == 0) return (-1); |
164 | x = mp_loadb(MP_NEW, q, g->g.noctets); |
165 | mp_div(0, &x, x, g->mm.m); mp_drop(*d); |
166 | *d = mpmont_mul(&g->mm, x, x, g->mm.r2); return(0); |
167 | } |
168 | |
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169 | /* --- @group_prime@ --- * |
170 | * |
171 | * Arguments: @const gprime_param *gp@ = group parameters |
172 | * |
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173 | * Returns: A pointer to the group, or null. |
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174 | * |
175 | * Use: Constructs an abstract group interface for a subgroup of a |
176 | * prime field. Group elements are @mp *@ pointers. |
177 | */ |
178 | |
179 | static const group_ops gops = { |
180 | GTY_PRIME, |
181 | gdestroygroup, gcreate, gcopy, gburn, gdestroy, |
182 | gsamep, geq, group_stdidentp, |
183 | gcheck, |
184 | gmul, gsqr, ginv, group_stddiv, gexp, gmexp, |
185 | gread, gwrite, |
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186 | gtoint, gfromint, group_stdtoec, group_stdfromec, gtobuf, gfrombuf, |
187 | gtoraw, gfromraw |
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188 | }; |
189 | |
190 | group *group_prime(const gprime_param *gp) |
191 | { |
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192 | gctx *g; |
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193 | |
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194 | if (!MP_ISPOS(gp->p) || !MP_ISODD(gp->p)) |
195 | return (0); |
196 | g = CREATE(gctx); |
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197 | g->g.ops = &gops; |
198 | g->g.nbits = mp_bits(gp->p); |
199 | g->g.noctets = (g->g.nbits + 7) >> 3; |
200 | mpmont_create(&g->mm, gp->p); |
201 | g->g.i = &g->mm.r; |
202 | g->gen = mpmont_mul(&g->mm, MP_NEW, gp->g, g->mm.r2); |
203 | g->g.g = &g->gen; |
204 | g->g.r = MP_COPY(gp->q); |
205 | g->g.h = MP_NEW; mp_div(&g->g.h, 0, gp->p, gp->q); |
206 | return (&g->g); |
207 | } |
208 | |
209 | /*----- That's all, folks -------------------------------------------------*/ |