| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: g-prime.c,v 1.3 2004/04/04 19:04:11 mdw Exp $ |
| 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 $ |
| 33 | * Revision 1.3 2004/04/04 19:04:11 mdw |
| 34 | * Raw I/O of elliptic curve points and group elements. |
| 35 | * |
| 36 | * Revision 1.2 2004/04/03 03:32:05 mdw |
| 37 | * General robustification. |
| 38 | * |
| 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 | |
| 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 | } |
| 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); |
| 151 | mp_div(0, &x, x, g->mm.m); mp_drop(*d); |
| 152 | *d = mpmont_mul(&g->mm, x, x, g->mm.r2); return(0); |
| 153 | } |
| 154 | |
| 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 | |
| 169 | /* --- @group_prime@ --- * |
| 170 | * |
| 171 | * Arguments: @const gprime_param *gp@ = group parameters |
| 172 | * |
| 173 | * Returns: A pointer to the group, or null. |
| 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, |
| 186 | gtoint, gfromint, group_stdtoec, group_stdfromec, gtobuf, gfrombuf, |
| 187 | gtoraw, gfromraw |
| 188 | }; |
| 189 | |
| 190 | group *group_prime(const gprime_param *gp) |
| 191 | { |
| 192 | gctx *g; |
| 193 | |
| 194 | if (!MP_ISPOS(gp->p) || !MP_ISODD(gp->p)) |
| 195 | return (0); |
| 196 | g = CREATE(gctx); |
| 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 -------------------------------------------------*/ |