3 * Abstraction for prime groups
5 * (c) 2004 Straylight/Edgeware
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of Catacomb.
12 * Catacomb is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU Library General Public License as
14 * published by the Free Software Foundation; either version 2 of the
15 * License, or (at your option) any later version.
17 * Catacomb is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU Library General Public License for more details.
22 * You should have received a copy of the GNU Library General Public
23 * License along with Catacomb; if not, write to the Free
24 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
28 /*----- Header files ------------------------------------------------------*/
36 #include "group-guts.h"
38 /*----- Main code ---------------------------------------------------------*/
40 /* --- Group operations --- */
42 static void gdestroygroup(group
*gg
) {
43 gctx_prime
*g
= (gctx_prime
*)gg
;
44 mp_drop(g
->gen
.x
); mp_drop(g
->g
.r
); mp_drop(g
->g
.h
);
45 mpmont_destroy(&g
->mm
);
49 static ge_prime
*gcreate(group
*gg
) {
50 gctx_prime
*g
= (gctx_prime
*)gg
; ge_prime
*x
= CREATE(ge_prime
);
51 x
->x
= MP_COPY(g
->i
.x
); return (x
);
54 static void gcopy(group
*gg
, ge_prime
*d
, ge_prime
*x
)
55 { mp
*t
= MP_COPY(x
->x
); MP_DROP(d
->x
); d
->x
= t
; }
57 static void gburn(group
*gg
, ge_prime
*x
) { x
->x
->f
|= MP_BURN
; }
59 static void gdestroy(group
*gg
, ge_prime
*x
) { MP_DROP(x
->x
); DESTROY(x
); }
61 static int gsamep(group
*gg
, group
*hh
) {
62 gctx_prime
*g
= (gctx_prime
*)gg
, *h
= (gctx_prime
*)hh
;
63 return (MP_EQ(g
->mm
.m
, h
->mm
.m
));
66 static int geq(group
*gg
, ge_prime
*x
, ge_prime
*y
)
67 { return (MP_EQ(x
->x
, y
->x
)); }
69 static const char *gcheck(group
*gg
, grand
*gr
) {
70 gctx_prime
*g
= (gctx_prime
*)gg
; int rc
; mp
*t
;
71 if (!pgen_primep(g
->mm
.m
, gr
)) return ("p is not prime");
72 t
= mp_mul(MP_NEW
, g
->g
.r
, g
->g
.h
); t
= mp_add(t
, t
, MP_ONE
);
73 rc
= MP_EQ(t
, g
->mm
.m
); MP_DROP(t
); if (!rc
) return ("not a subgroup");
74 return (group_stdcheck(gg
, gr
));
77 static void gmul(group
*gg
, ge_prime
*d
, ge_prime
*x
, ge_prime
*y
) {
78 gctx_prime
*g
= (gctx_prime
*)gg
;
79 d
->x
= mpmont_mul(&g
->mm
, d
->x
, x
->x
, y
->x
);
82 static void gsqr(group
*gg
, ge_prime
*d
, ge_prime
*x
) {
83 gctx_prime
*g
= (gctx_prime
*)gg
; mp
*r
= mp_sqr(d
->x
, x
->x
);
84 d
->x
= mpmont_reduce(&g
->mm
, r
, r
);
87 static void ginv(group
*gg
, ge_prime
*d
, ge_prime
*x
) {
88 gctx_prime
*g
= (gctx_prime
*)gg
;
89 mp
*r
= mpmont_reduce(&g
->mm
, d
->x
, x
->x
);
90 r
= mp_modinv(r
, r
, g
->mm
.m
); d
->x
= mpmont_mul(&g
->mm
, r
, r
, g
->mm
.r2
);
93 static void gexp(group
*gg
, ge_prime
*d
, ge_prime
*x
, mp
*n
)
95 gctx_prime
*g
= (gctx_prime
*)gg
;
96 d
->x
= mpmont_expr(&g
->mm
, d
->x
, x
->x
, n
);
99 static void gmexp(group
*gg
, ge_prime
*d
, const group_expfactor
*f
, size_t n
)
101 gctx_prime
*g
= (gctx_prime
*)gg
; size_t i
;
102 mp_expfactor
*ff
= xmalloc(n
* sizeof(mp_expfactor
));
103 for (i
= 0; i
< n
; i
++)
104 { ff
[i
].base
= f
[i
].base
->x
; ff
[i
].exp
= f
[i
].exp
; }
105 d
->x
= mpmont_mexpr(&g
->mm
, d
->x
, ff
, n
); xfree(ff
);
108 static int gread(group
*gg
, ge_prime
*d
, const mptext_ops
*ops
, void *p
) {
109 gctx_prime
*g
= (gctx_prime
*)gg
; mp
*t
;
110 if ((t
= mp_read(MP_NEW
, 0, ops
, p
)) == 0) return (-1);
111 mp_drop(d
->x
); d
->x
= mpmont_mul(&g
->mm
, t
, t
, g
->mm
.r2
); return (0);
114 static int gwrite(group
*gg
, ge_prime
*x
, const mptext_ops
*ops
, void *p
) {
115 gctx_prime
*g
= (gctx_prime
*)gg
;
116 mp
*t
= mpmont_reduce(&g
->mm
, MP_NEW
, x
->x
);
117 int rc
= mp_write(t
, 10, ops
, p
); MP_DROP(t
); return (rc
);
120 static mp
*gtoint(group
*gg
, mp
*d
, ge_prime
*x
) {
121 gctx_prime
*g
= (gctx_prime
*)gg
;
122 return (mpmont_reduce(&g
->mm
, d
, x
->x
));
125 static int gfromint(group
*gg
, ge_prime
*d
, mp
*x
) {
126 gctx_prime
*g
= (gctx_prime
*)gg
; mp_div(0, &d
->x
, x
, g
->mm
.m
);
127 d
->x
= mpmont_mul(&g
->mm
, d
->x
, d
->x
, g
->mm
.r2
); return (0);
130 static int gtobuf(group
*gg
, buf
*b
, ge_prime
*x
) {
131 gctx_prime
*g
= (gctx_prime
*)gg
;
132 mp
*t
= mpmont_reduce(&g
->mm
, MP_NEW
, x
->x
);
133 int rc
= buf_putmp(b
, t
); MP_DROP(t
); return (rc
);
136 static int gfrombuf(group
*gg
, buf
*b
, ge_prime
*d
) {
137 gctx_prime
* g
= (gctx_prime
*)gg
; mp
*x
;
138 if ((x
= buf_getmp(b
)) == 0) return (-1);
139 mp_div(0, &x
, x
, g
->mm
.m
); mp_drop(d
->x
);
140 d
->x
= mpmont_mul(&g
->mm
, x
, x
, g
->mm
.r2
); return(0);
143 static int gtoraw(group
*gg
, buf
*b
, ge_prime
*x
) {
144 gctx_prime
*g
= (gctx_prime
*)gg
; octet
*q
;
145 mp
*t
= mpmont_reduce(&g
->mm
, MP_NEW
, x
->x
);
146 if ((q
= buf_get(b
, g
->g
.noctets
)) == 0) { MP_DROP(t
); return (-1); }
147 mp_storeb(t
, q
, g
->g
.noctets
); MP_DROP(t
); return (0);
150 static int gfromraw(group
*gg
, buf
*b
, ge_prime
*d
) {
151 gctx_prime
* g
= (gctx_prime
*)gg
; mp
*x
; octet
*q
;
152 if ((q
= buf_get(b
, g
->g
.noctets
)) == 0) return (-1);
153 x
= mp_loadb(MP_NEW
, q
, g
->g
.noctets
);
154 mp_div(0, &x
, x
, g
->mm
.m
); mp_drop(d
->x
);
155 d
->x
= mpmont_mul(&g
->mm
, x
, x
, g
->mm
.r2
); return(0);
158 /* --- @group_prime@ --- *
160 * Arguments: @const gprime_param *gp@ = group parameters
162 * Returns: A pointer to the group, or null.
164 * Use: Constructs an abstract group interface for a subgroup of a
165 * prime field. Group elements are @mp *@ pointers.
168 static const group_ops gops
= {
170 gdestroygroup
, gcreate
, gcopy
, gburn
, gdestroy
,
171 gsamep
, geq
, group_stdidentp
,
173 gmul
, gsqr
, ginv
, group_stddiv
, gexp
, gmexp
,
175 gtoint
, gfromint
, group_stdtoec
, group_stdfromec
, gtobuf
, gfrombuf
,
179 group
*group_prime(const gprime_param
*gp
)
183 if (!MP_POSP(gp
->p
) || !MP_ODDP(gp
->p
))
185 g
= CREATE(gctx_prime
);
187 g
->g
.nbits
= mp_bits(gp
->p
);
188 g
->g
.noctets
= (g
->g
.nbits
+ 7) >> 3;
189 mpmont_create(&g
->mm
, gp
->p
);
190 g
->i
.x
= g
->mm
.r
; g
->g
.i
= &g
->i
;
191 g
->gen
.x
= mpmont_mul(&g
->mm
, MP_NEW
, gp
->g
, g
->mm
.r2
);
193 g
->g
.r
= MP_COPY(gp
->q
);
194 g
->g
.h
= MP_NEW
; mp_div(&g
->g
.h
, 0, gp
->p
, gp
->q
);
198 /*----- That's all, folks -------------------------------------------------*/