3 * $Id: f-prime.c,v 1.3 2003/05/15 23:25:59 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 1.3 2003/05/15 23:25:59 mdw
34 * Make elliptic curve stuff build.
36 * Revision 1.2 2002/01/13 13:48:44 mdw
39 * Revision 1.1 2001/04/29 18:12:33 mdw
44 /*----- Header files ------------------------------------------------------*/
51 /*----- Data structures ---------------------------------------------------*/
58 /*----- Main code ---------------------------------------------------------*/
60 /* --- Field operations --- */
62 static void fdestroy(field *ff)
65 mpmont_destroy(&f->mm);
69 static mp *fin(field *ff, mp *d, mp *x)
72 return (mpmont_mul(&f->mm, d, x, f->mm.r2));
75 static mp *fout(field *ff, mp *d, mp *x)
78 return (mpmont_reduce(&f->mm, d, x));
81 static mp *fneg(field *ff, mp *d, mp *x)
84 return (mp_sub(d, f->mm.m, x));
87 static mp *fadd(field *ff, mp *d, mp *x, mp *y)
89 return (mp_add(d, x, y));
92 static mp *fsub(field *ff, mp *d, mp *x, mp *y)
94 return (mp_sub(d, x, y));
97 static mp *fmul(field *ff, mp *d, mp *x, mp *y)
100 return (mpmont_mul(&f->mm, d, x, y));
103 static mp *fsqr(field *ff, mp *d, mp *x)
105 fctx *f = (fctx *)ff;
107 return (mpmont_reduce(&f->mm, d, d));
110 static mp *finv(field *ff, mp *d, mp *x)
112 fctx *f = (fctx *)ff;
113 d = mpmont_reduce(&f->mm, d, x);
114 mp_gcd(0, 0, &d, f->mm.m, d);
115 return (mpmont_mul(&f->mm, d, d, f->mm.r2));
118 static mp *freduce(field *ff, mp *d, mp *x)
120 fctx *f = (fctx *)ff;
121 mp_div(0, &d, x, f->mm.m);
125 static mp *fdbl(field *ff, mp *d, mp *x)
127 /* fctx *f = (fctx *)ff; */
128 return (mp_lsl(d, x, 1));
131 static mp *ftpl(field *ff, mp *d, mp *x)
133 /* fctx *f = (fctx *)ff; */
134 MP_DEST(d, MP_LEN(x) + 1, x->f);
135 MPX_UMULN(d->v, d->vl, x->v, x->vl, 3);
139 static mp *fsqrt(field *ff, mp *d, mp *x)
141 fctx *f = (fctx *)ff;
142 d = mpmont_reduce(&f->mm, d, x);
143 d = mp_modsqrt(d, d, f->mm.m);
144 return (mpmont_mul(&f->mm, d, d, f->mm.r2));
147 /* --- Field operations table --- */
149 static field_ops fops = {
152 fneg, fadd, fsub, fmul, fsqr, finv, freduce,
156 /* --- @field_prime@ --- *
158 * Arguments: @mp *p@ = the characteristic of the field
160 * Returns: A pointer to the field.
162 * Use: Creates a field structure for a prime field of size %$p$%,
163 * using Montgomery reduction for arithmetic.
166 field *field_prime(mp *p)
168 fctx *f = CREATE(fctx);
170 mpmont_create(&f->mm, p);
176 /*----- That's all, folks -------------------------------------------------*/