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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: f-prime.c,v 1.2 2002/01/13 13:48:44 mdw Exp $ |
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4 | * |
5 | * Prime fields with Montgomery arithmetic |
6 | * |
7 | * (c) 2001 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of Catacomb. |
13 | * |
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. |
18 | * |
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. |
23 | * |
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, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: f-prime.c,v $ |
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33 | * Revision 1.2 2002/01/13 13:48:44 mdw |
34 | * Further progress. |
35 | * |
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36 | * Revision 1.1 2001/04/29 18:12:33 mdw |
37 | * Prototype version. |
38 | * |
39 | */ |
40 | |
41 | /*----- Header files ------------------------------------------------------*/ |
42 | |
43 | #include <mLib/sub.h> |
44 | |
45 | #include "field.h" |
46 | #include "mpmont.h" |
47 | |
48 | /*----- Data structures ---------------------------------------------------*/ |
49 | |
50 | typedef struct fctx { |
51 | field f; |
52 | mpmont mm; |
53 | } fctx; |
54 | |
55 | /*----- Main code ---------------------------------------------------------*/ |
56 | |
57 | /* --- Field operations --- */ |
58 | |
59 | static void fdestroy(field *ff) |
60 | { |
61 | fctx *f = (fctx *)ff; |
62 | mpmont_destroy(&f->mm); |
63 | DESTROY(f); |
64 | } |
65 | |
66 | static mp *fin(field *ff, mp *d, mp *x) |
67 | { |
68 | fctx *f = (fctx *)ff; |
69 | return (mpmont_mul(&f->mm, d, x, f->mm.r2)); |
70 | } |
71 | |
72 | static mp *fout(field *ff, mp *d, mp *x) |
73 | { |
74 | fctx *f = (fctx *)ff; |
75 | return (mpmont_reduce(&f->mm, d, x)); |
76 | } |
77 | |
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78 | static mp *fneg(field *ff, mp *d, mp *x) |
79 | { |
80 | fctx *f = (fctx *)ff; |
81 | return (mp_sub(d, f->mm.m, x)); |
82 | } |
83 | |
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84 | static mp *fadd(field *ff, mp *d, mp *x, mp *y) |
85 | { |
86 | return (mp_add(d, x, y)); |
87 | } |
88 | |
89 | static mp *fsub(field *ff, mp *d, mp *x, mp *y) |
90 | { |
91 | return (mp_sub(d, x, y)); |
92 | } |
93 | |
94 | static mp *fmul(field *ff, mp *d, mp *x, mp *y) |
95 | { |
96 | fctx *f = (fctx *)ff; |
97 | return (mpmont_mul(&f->mm, d, x, y)); |
98 | } |
99 | |
100 | static mp *fsqr(field *ff, mp *d, mp *x) |
101 | { |
102 | fctx *f = (fctx *)ff; |
103 | d = mp_sqr(d, x); |
104 | return (mpmont_reduce(&f->mm, d, d)); |
105 | } |
106 | |
107 | static mp *finv(field *ff, mp *d, mp *x) |
108 | { |
109 | fctx *f = (fctx *)ff; |
110 | d = mpmont_reduce(&f->mm, x); |
111 | mp_gcd(0, 0, &d, f->mm.m, d); |
112 | return (mpmont_mul(&f->mm, d, d, f->mm.r2)); |
113 | } |
114 | |
115 | static mp *freduce(field *ff, mp *d, mp *x) |
116 | { |
117 | fctx *f = (fctx *)ff; |
118 | mp_div(0, &d, x, f->mm.m); |
119 | return (d); |
120 | } |
121 | |
122 | static mp *fdbl(field *ff, mp *d, mp *x) |
123 | { |
124 | fctx *f = (fctx *)ff; |
125 | return (mp_lsl(d, x, 1)); |
126 | } |
127 | |
128 | static mp *ftpl(field *ff, mp *d, mp *x) |
129 | { |
130 | fctx *f = (fctx *)ff; |
131 | MP_DEST(d, MP_LEN(x) + 1, x->f); |
132 | MPX_UMULN(d->v, d->vl, x->v, x->vl, 3); |
133 | return (d); |
134 | } |
135 | |
136 | static mp *fsqrt(field *ff, mp *d, mp *x) |
137 | { |
138 | fctx *f = (fctx *)ff; |
139 | d = mpmont_reduce(&f->mm, x); |
140 | d = mp_modsqrt(d, d, f->mm.m); |
141 | return (mpmont_mul(&f->mm, d, d, f->mm.r2)); |
142 | } |
143 | |
144 | /* --- Field operations table --- */ |
145 | |
146 | static field_ops fops = { |
147 | fdestroy, |
148 | fin, fout, |
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149 | fneg, fadd, fsub, fmul, fsqr, finv, freduce, |
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150 | fdbl, ftpl, fsqrt |
151 | }; |
152 | |
153 | /* --- @field_prime@ --- * |
154 | * |
155 | * Arguments: @mp *p@ = the characteristic of the field |
156 | * |
157 | * Returns: A pointer to the field. |
158 | * |
159 | * Use: Creates a field structure for a prime field of size %$p$%, |
160 | * using Montgomery reduction for arithmetic. |
161 | */ |
162 | |
163 | field *field_prime(mp *p) |
164 | { |
165 | ftcx *f = CREATE(fctx); |
166 | f->f.ops = &fops; |
167 | mpmont_create(&f->mm, p); |
168 | f->zero = MP_ZERO; |
169 | f->one = &f->mm.r; |
170 | return (&f->f); |
171 | } |
172 | |
173 | /*----- That's all, folks -------------------------------------------------*/ |