3 * $Id: f-prime.c,v 1.1 2001/04/29 18:12:33 mdw Exp $
5 * Prime fields with Montgomery arithmetic
7 * (c) 2001 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 /*----- Revision history --------------------------------------------------*
33 * Revision 1.1 2001/04/29 18:12:33 mdw
38 /*----- Header files ------------------------------------------------------*/
45 /*----- Data structures ---------------------------------------------------*/
52 /*----- Main code ---------------------------------------------------------*/
54 /* --- Field operations --- */
56 static void fdestroy(field
*ff
)
59 mpmont_destroy(&f
->mm
);
63 static mp
*fin(field
*ff
, mp
*d
, mp
*x
)
66 return (mpmont_mul(&f
->mm
, d
, x
, f
->mm
.r2
));
69 static mp
*fout(field
*ff
, mp
*d
, mp
*x
)
72 return (mpmont_reduce(&f
->mm
, d
, x
));
75 static mp
*fadd(field
*ff
, mp
*d
, mp
*x
, mp
*y
)
77 return (mp_add(d
, x
, y
));
80 static mp
*fsub(field
*ff
, mp
*d
, mp
*x
, mp
*y
)
82 return (mp_sub(d
, x
, y
));
85 static mp
*fmul(field
*ff
, mp
*d
, mp
*x
, mp
*y
)
88 return (mpmont_mul(&f
->mm
, d
, x
, y
));
91 static mp
*fsqr(field
*ff
, mp
*d
, mp
*x
)
95 return (mpmont_reduce(&f
->mm
, d
, d
));
98 static mp
*finv(field
*ff
, mp
*d
, mp
*x
)
100 fctx
*f
= (fctx
*)ff
;
101 d
= mpmont_reduce(&f
->mm
, x
);
102 mp_gcd(0, 0, &d
, f
->mm
.m
, d
);
103 return (mpmont_mul(&f
->mm
, d
, d
, f
->mm
.r2
));
106 static mp
*freduce(field
*ff
, mp
*d
, mp
*x
)
108 fctx
*f
= (fctx
*)ff
;
109 mp_div(0, &d
, x
, f
->mm
.m
);
113 static mp
*fdbl(field
*ff
, mp
*d
, mp
*x
)
115 fctx
*f
= (fctx
*)ff
;
116 return (mp_lsl(d
, x
, 1));
119 static mp
*ftpl(field
*ff
, mp
*d
, mp
*x
)
121 fctx
*f
= (fctx
*)ff
;
122 MP_DEST(d
, MP_LEN(x
) + 1, x
->f
);
123 MPX_UMULN(d
->v
, d
->vl
, x
->v
, x
->vl
, 3);
127 static mp
*fsqrt(field
*ff
, mp
*d
, mp
*x
)
129 fctx
*f
= (fctx
*)ff
;
130 d
= mpmont_reduce(&f
->mm
, x
);
131 d
= mp_modsqrt(d
, d
, f
->mm
.m
);
132 return (mpmont_mul(&f
->mm
, d
, d
, f
->mm
.r2
));
135 /* --- Field operations table --- */
137 static field_ops fops
= {
140 fadd
, fsub
, fmul
, fsqr
, finv
, freduce
,
144 /* --- @field_prime@ --- *
146 * Arguments: @mp *p@ = the characteristic of the field
148 * Returns: A pointer to the field.
150 * Use: Creates a field structure for a prime field of size %$p$%,
151 * using Montgomery reduction for arithmetic.
154 field
*field_prime(mp
*p
)
156 ftcx
*f
= CREATE(fctx
);
158 mpmont_create(&f
->mm
, p
);
164 /*----- That's all, folks -------------------------------------------------*/