3 * $Id: group-stdops.c,v 1.3 2004/04/17 09:58:37 mdw Exp $
5 * Standard group operations
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 ------------------------------------------------------*/
35 /*----- Handy functions ---------------------------------------------------*/
37 /* --- @group_check@ --- *
39 * Arguments: @group *g@ = an abstract group
40 * @ge *x@ = a group element
42 * Returns: Zero on success, nonzero for failure.
44 * Use: Checks that @x@ is a valid group element. This may take a
45 * while, since it checks that %$x \ne 1$% and %$x^r = 1$%.
48 int group_check(group
*g
, ge
*x
)
54 rc
= (G_IDENTP(g
, d
) && !G_IDENTP(g
, x
));
60 /* --- @group_samep@ --- *
62 * Arguments: @group *g, *h@ = two abstract groups
64 * Returns: Nonzero if the groups are in fact identical (not just
67 * Use: Checks to see whether two groups are actually the same. This
68 * function does the full check: the group operatrion @samep@
69 * just does the group-specific details.
72 int group_samep(group
*g
, group
*h
)
74 return (g
->ops
== h
->ops
&&
75 MP_EQ(g
->r
, h
->r
) && MP_EQ(g
->h
, h
->h
) &&
76 G_EQ(g
, g
->i
, h
->i
) && G_EQ(g
, g
->g
, h
->g
) &&
80 /*----- Standard implementations ------------------------------------------*/
82 /* --- @group_stdidentp@ --- *
84 * Arguments: @group *g@ = abstract group
85 * @ge *x@ = group element
87 * Returns: Nonzero if %$x$% is the group identity.
90 int group_stdidentp(group
*g
, ge
*x
) { return (G_EQ(g
, x
, g
->i
)); }
92 /* --- @group_stdsqr@ --- *
94 * Arguments: @group *g@ = abstract group
95 * @ge *d@ = destination pointer
96 * @ge *x@ = group element
100 * Use: Computes %$d = x^2$% as %$d = x x$%.
103 void group_stdsqr(group
*g
, ge
*d
, ge
*x
) { G_MUL(g
, d
, x
, x
); }
105 /* --- @group_stddiv@ --- *
107 * Arguments: @group *g@ = abstract group
108 * @ge *d@ = destination pointer
114 * Use: Computes %$d = x/y$% as %$d = x y^{-1}$%.
117 void group_stddiv(group
*g
, ge
*d
, ge
*x
, ge
*y
)
123 /* --- @group_stdtoec@ --- *
125 * Arguments: @group *g@ = abstract group
126 * @ec *d@ = destination point
127 * @ge *x@ = group element
129 * Returns: @-1@, indicating failure.
131 * Use: Fails to convert a group element to an elliptic curve point.
134 int group_stdtoec(group
*g
, ec
*d
, ge
*x
) { return (-1); }
136 /* --- @group_stdfromec@ --- *
138 * Arguments: @group *g@ = abstract group
139 * @ge *d@ = destination pointer
140 * @const ec *p@ = elliptic curve point
142 * Returns: Zero for success, @-1@ on failure.
144 * Use: Converts %$p$% to a group element by converting its %$x$%-
148 int group_stdfromec(group
*g
, ge
*d
, const ec
*p
)
149 { if (EC_ATINF(p
)) return (-1); return (G_FROMINT(g
, d
, p
->x
)); }
151 /* --- @group_stdcheck@ --- *
153 * Arguments: @group *g@ = abstract group
154 * @grand *gr@ = random number source.
156 * Returns: Null on success, or a pointer to an error message.
159 const char *group_stdcheck(group
*g
, grand
*gr
)
164 if (!pgen_primep(g
->r
, gr
)) return ("group order not prime");
165 t
= G_CREATE(g
); G_EXP(g
, t
, g
->g
, g
->r
);
166 rc
= G_IDENTP(g
, t
); G_DESTROY(g
, t
);
167 if (!rc
) return ("generator not in the group");
171 /*----- That's all, folks -------------------------------------------------*/