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 ------------------------------------------------------*/
39 #include "group-guts.h"
41 /*----- Main code ---------------------------------------------------------*/
43 /* --- Group operations --- */
45 static void gdestroygroup(group
*gg
) {
46 gctx_prime
*g
= (gctx_prime
*)gg
;
47 mp_drop(g
->gen
); mp_drop(g
->g
.r
); mp_drop(g
->g
.h
);
48 mpmont_destroy(&g
->mm
);
52 static mp
**gcreate(group
*gg
)
53 { mp
**x
= CREATE(mp
*); *x
= MP_COPY(*gg
->i
); return (x
); }
55 static void gcopy(group
*gg
, mp
**d
, mp
**x
)
56 { mp
*t
= MP_COPY(*x
); MP_DROP(*d
); *d
= t
; }
58 static void gburn(group
*gg
, mp
**x
) { (*x
)->f
|= MP_BURN
; }
60 static void gdestroy(group
*gg
, mp
**x
) { MP_DROP(*x
); DESTROY(x
); }
62 static int gsamep(group
*gg
, group
*hh
) {
63 gctx_prime
*g
= (gctx_prime
*)gg
, *h
= (gctx_prime
*)hh
;
64 return (MP_EQ(g
->mm
.m
, h
->mm
.m
));
67 static int geq(group
*gg
, mp
**x
, mp
**y
) { return (MP_EQ(*x
, *y
)); }
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
, mp
**d
, mp
**x
, mp
**y
)
78 { gctx_prime
*g
= (gctx_prime
*)gg
; *d
= mpmont_mul(&g
->mm
, *d
, *x
, *y
); }
80 static void gsqr(group
*gg
, mp
**d
, mp
**x
) {
81 gctx_prime
*g
= (gctx_prime
*)gg
; mp
*r
= mp_sqr(*d
, *x
);
82 *d
= mpmont_reduce(&g
->mm
, r
, r
);
85 static void ginv(group
*gg
, mp
**d
, mp
**x
) {
86 gctx_prime
*g
= (gctx_prime
*)gg
; mp
*r
= mpmont_reduce(&g
->mm
, *d
, *x
);
87 r
= mp_modinv(r
, r
, g
->mm
.m
); *d
= mpmont_mul(&g
->mm
, r
, r
, g
->mm
.r2
);
90 static void gexp(group
*gg
, mp
**d
, mp
**x
, mp
*n
)
91 { gctx_prime
*g
= (gctx_prime
*)gg
; *d
= mpmont_expr(&g
->mm
, *d
, *x
, n
); }
93 static void gmexp(group
*gg
, mp
**d
, const group_expfactor
*f
, size_t n
) {
94 gctx_prime
*g
= (gctx_prime
*)gg
; size_t i
;
95 mp_expfactor
*ff
= xmalloc(n
* sizeof(mp_expfactor
));
96 for (i
= 0; i
< n
; i
++) { ff
[i
].base
= *f
[i
].base
; ff
[i
].exp
= f
[i
].exp
; }
97 *d
= mpmont_mexpr(&g
->mm
, *d
, ff
, n
); xfree(ff
);
100 static int gread(group
*gg
, mp
**d
, const mptext_ops
*ops
, void *p
) {
101 gctx_prime
*g
= (gctx_prime
*)gg
; mp
*t
;
102 if ((t
= mp_read(MP_NEW
, 0, ops
, p
)) == 0) return (-1);
103 mp_drop(*d
); *d
= mpmont_mul(&g
->mm
, t
, t
, g
->mm
.r2
); return (0);
106 static int gwrite(group
*gg
, mp
**x
, const mptext_ops
*ops
, void *p
) {
107 gctx_prime
*g
= (gctx_prime
*)gg
;
108 mp
*t
= mpmont_reduce(&g
->mm
, MP_NEW
, *x
);
109 int rc
= mp_write(t
, 10, ops
, p
); MP_DROP(t
); return (rc
);
112 static mp
*gtoint(group
*gg
, mp
*d
, mp
**x
) {
113 gctx_prime
*g
= (gctx_prime
*)gg
;
114 return (mpmont_reduce(&g
->mm
, d
, *x
));
117 static int gfromint(group
*gg
, mp
**d
, mp
*x
) {
118 gctx_prime
*g
= (gctx_prime
*)gg
; mp_div(0, d
, x
, g
->mm
.m
);
119 *d
= mpmont_mul(&g
->mm
, *d
, *d
, g
->mm
.r2
); return (0);
122 static int gtobuf(group
*gg
, buf
*b
, mp
**x
) {
123 gctx_prime
*g
= (gctx_prime
*)gg
;
124 mp
*t
= mpmont_reduce(&g
->mm
, MP_NEW
, *x
);
125 int rc
= buf_putmp(b
, t
); MP_DROP(t
); return (rc
);
128 static int gfrombuf(group
*gg
, buf
*b
, mp
**d
) {
129 gctx_prime
* g
= (gctx_prime
*)gg
; mp
*x
;
130 if ((x
= buf_getmp(b
)) == 0) return (-1);
131 mp_div(0, &x
, x
, g
->mm
.m
); mp_drop(*d
);
132 *d
= mpmont_mul(&g
->mm
, x
, x
, g
->mm
.r2
); return(0);
135 static int gtoraw(group
*gg
, buf
*b
, mp
**x
) {
136 gctx_prime
*g
= (gctx_prime
*)gg
; octet
*q
;
137 mp
*t
= mpmont_reduce(&g
->mm
, MP_NEW
, *x
);
138 if ((q
= buf_get(b
, g
->g
.noctets
)) == 0) { MP_DROP(t
); return (-1); }
139 mp_storeb(t
, q
, g
->g
.noctets
); MP_DROP(t
); return (0);
142 static int gfromraw(group
*gg
, buf
*b
, mp
**d
) {
143 gctx_prime
* g
= (gctx_prime
*)gg
; mp
*x
; octet
*q
;
144 if ((q
= buf_get(b
, g
->g
.noctets
)) == 0) return (-1);
145 x
= mp_loadb(MP_NEW
, q
, g
->g
.noctets
);
146 mp_div(0, &x
, x
, g
->mm
.m
); mp_drop(*d
);
147 *d
= mpmont_mul(&g
->mm
, x
, x
, g
->mm
.r2
); return(0);
150 /* --- @group_prime@ --- *
152 * Arguments: @const gprime_param *gp@ = group parameters
154 * Returns: A pointer to the group, or null.
156 * Use: Constructs an abstract group interface for a subgroup of a
157 * prime field. Group elements are @mp *@ pointers.
160 static const group_ops gops
= {
162 gdestroygroup
, gcreate
, gcopy
, gburn
, gdestroy
,
163 gsamep
, geq
, group_stdidentp
,
165 gmul
, gsqr
, ginv
, group_stddiv
, gexp
, gmexp
,
167 gtoint
, gfromint
, group_stdtoec
, group_stdfromec
, gtobuf
, gfrombuf
,
171 group
*group_prime(const gprime_param
*gp
)
175 if (!MP_POSP(gp
->p
) || !MP_ODDP(gp
->p
))
177 g
= CREATE(gctx_prime
);
179 g
->g
.nbits
= mp_bits(gp
->p
);
180 g
->g
.noctets
= (g
->g
.nbits
+ 7) >> 3;
181 mpmont_create(&g
->mm
, gp
->p
);
183 g
->gen
= mpmont_mul(&g
->mm
, MP_NEW
, gp
->g
, g
->mm
.r2
);
185 g
->g
.r
= MP_COPY(gp
->q
);
186 g
->g
.h
= MP_NEW
; mp_div(&g
->g
.h
, 0, gp
->p
, gp
->q
);
190 /*----- That's all, folks -------------------------------------------------*/