5 * Abstraction for prime groups
7 * (c) 2004 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 /*----- Header files ------------------------------------------------------*/
40 /*----- Data structures ---------------------------------------------------*/
48 /*----- Main code ---------------------------------------------------------*/
50 /* --- Group operations --- */
52 static void gdestroygroup(group *gg) {
54 mp_drop(g->gen); mp_drop(g->g.r); mp_drop(g->g.h);
55 mpmont_destroy(&g->mm);
59 static mp **gcreate(group *gg)
60 { mp **x = CREATE(mp *); *x = MP_COPY(*gg->i); return (x); }
62 static void gcopy(group *gg, mp **d, mp **x)
63 { mp *t = MP_COPY(*x); MP_DROP(*d); *d = t; }
65 static void gburn(group *gg, mp **x) { (*x)->f |= MP_BURN; }
67 static void gdestroy(group *gg, mp **x) { MP_DROP(*x); DESTROY(x); }
69 static int gsamep(group *gg, group *hh) {
70 gctx *g = (gctx *)gg, *h = (gctx *)hh;
71 return (MP_EQ(g->mm.m, h->mm.m));
74 static int geq(group *gg, mp **x, mp **y) { return (MP_EQ(*x, *y)); }
76 static const char *gcheck(group *gg, grand *gr) {
77 gctx *g = (gctx *)gg; int rc; mp *t;
78 if (!pgen_primep(g->mm.m, gr)) return ("p is not prime");
79 t = mp_mul(MP_NEW, g->g.r, g->g.h); t = mp_add(t, t, MP_ONE);
80 rc = MP_EQ(t, g->mm.m); MP_DROP(t); if (!rc) return ("not a subgroup");
81 return (group_stdcheck(gg, gr));
84 static void gmul(group *gg, mp **d, mp **x, mp **y)
85 { gctx *g = (gctx *)gg; *d = mpmont_mul(&g->mm, *d, *x, *y); }
87 static void gsqr(group *gg, mp **d, mp **x) {
88 gctx *g = (gctx *)gg; mp *r = mp_sqr(*d, *x);
89 *d = mpmont_reduce(&g->mm, r, r);
92 static void ginv(group *gg, mp **d, mp **x) {
93 gctx *g = (gctx *)gg; mp *r = mpmont_reduce(&g->mm, *d, *x);
94 r = mp_modinv(r, r, g->mm.m); *d = mpmont_mul(&g->mm, r, r, g->mm.r2);
97 static void gexp(group *gg, mp **d, mp **x, mp *n)
98 { gctx *g = (gctx *)gg; *d = mpmont_expr(&g->mm, *d, *x, n); }
100 static void gmexp(group *gg, mp **d, const group_expfactor *f, size_t n) {
101 gctx *g = (gctx *)gg; size_t i;
102 mp_expfactor *ff = xmalloc(n * sizeof(mp_expfactor));
103 for (i = 0; i < n; i++) { ff[i].base = *f[i].base; ff[i].exp = f[i].exp; }
104 *d = mpmont_mexpr(&g->mm, *d, ff, n); xfree(ff);
107 static int gread(group *gg, mp **d, const mptext_ops *ops, void *p) {
108 gctx *g = (gctx *)gg; mp *t;
109 if ((t = mp_read(MP_NEW, 0, ops, p)) == 0) return (-1);
110 mp_drop(*d); *d = mpmont_mul(&g->mm, t, t, g->mm.r2); return (0);
113 static int gwrite(group *gg, mp **x, const mptext_ops *ops, void *p) {
114 gctx *g = (gctx *)gg; mp *t = mpmont_reduce(&g->mm, MP_NEW, *x);
115 int rc = mp_write(t, 10, ops, p); MP_DROP(t); return (rc);
118 static mp *gtoint(group *gg, mp *d, mp **x)
119 { gctx *g = (gctx *)gg; return (mpmont_reduce(&g->mm, d, *x)); }
121 static int gfromint(group *gg, mp **d, mp *x) {
122 gctx *g = (gctx *)gg; mp_div(0, d, x, g->mm.m);
123 *d = mpmont_mul(&g->mm, *d, *d, g->mm.r2); return (0);
126 static int gtobuf(group *gg, buf *b, mp **x) {
127 gctx *g = (gctx *)gg; mp *t = mpmont_reduce(&g->mm, MP_NEW, *x);
128 int rc = buf_putmp(b, t); MP_DROP(t); return (rc);
131 static int gfrombuf(group *gg, buf *b, mp **d) {
132 gctx * g = (gctx *)gg; mp *x; if ((x = buf_getmp(b)) == 0) return (-1);
133 mp_div(0, &x, x, g->mm.m); mp_drop(*d);
134 *d = mpmont_mul(&g->mm, x, x, g->mm.r2); return(0);
137 static int gtoraw(group *gg, buf *b, mp **x) {
138 gctx *g = (gctx *)gg; octet *q; mp *t = mpmont_reduce(&g->mm, MP_NEW, *x);
139 if ((q = buf_get(b, g->g.noctets)) == 0) { MP_DROP(t); return (-1); }
140 mp_storeb(t, q, g->g.noctets); MP_DROP(t); return (0);
143 static int gfromraw(group *gg, buf *b, mp **d) {
144 gctx * g = (gctx *)gg; mp *x; octet *q;
145 if ((q = buf_get(b, g->g.noctets)) == 0) return (-1);
146 x = mp_loadb(MP_NEW, q, g->g.noctets);
147 mp_div(0, &x, x, g->mm.m); mp_drop(*d);
148 *d = mpmont_mul(&g->mm, x, x, g->mm.r2); return(0);
151 /* --- @group_prime@ --- *
153 * Arguments: @const gprime_param *gp@ = group parameters
155 * Returns: A pointer to the group, or null.
157 * Use: Constructs an abstract group interface for a subgroup of a
158 * prime field. Group elements are @mp *@ pointers.
161 static const group_ops gops = {
163 gdestroygroup, gcreate, gcopy, gburn, gdestroy,
164 gsamep, geq, group_stdidentp,
166 gmul, gsqr, ginv, group_stddiv, gexp, gmexp,
168 gtoint, gfromint, group_stdtoec, group_stdfromec, gtobuf, gfrombuf,
172 group *group_prime(const gprime_param *gp)
176 if (!MP_POSP(gp->p) || !MP_ODDP(gp->p))
180 g->g.nbits = mp_bits(gp->p);
181 g->g.noctets = (g->g.nbits + 7) >> 3;
182 mpmont_create(&g->mm, gp->p);
184 g->gen = mpmont_mul(&g->mm, MP_NEW, gp->g, g->mm.r2);
186 g->g.r = MP_COPY(gp->q);
187 g->g.h = MP_NEW; mp_div(&g->g.h, 0, gp->p, gp->q);
191 /*----- That's all, folks -------------------------------------------------*/