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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: f-prime.c,v 1.3 2003/05/15 23:25:59 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 1.3 2003/05/15 23:25:59 mdw |
34 | * Make elliptic curve stuff build. |
35 | * |
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36 | * Revision 1.2 2002/01/13 13:48:44 mdw |
37 | * Further progress. |
38 | * |
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39 | * Revision 1.1 2001/04/29 18:12:33 mdw |
40 | * Prototype version. |
41 | * |
42 | */ |
43 | |
44 | /*----- Header files ------------------------------------------------------*/ |
45 | |
46 | #include <mLib/sub.h> |
47 | |
48 | #include "field.h" |
49 | #include "mpmont.h" |
50 | |
51 | /*----- Data structures ---------------------------------------------------*/ |
52 | |
53 | typedef struct fctx { |
54 | field f; |
55 | mpmont mm; |
56 | } fctx; |
57 | |
58 | /*----- Main code ---------------------------------------------------------*/ |
59 | |
60 | /* --- Field operations --- */ |
61 | |
62 | static void fdestroy(field *ff) |
63 | { |
64 | fctx *f = (fctx *)ff; |
65 | mpmont_destroy(&f->mm); |
66 | DESTROY(f); |
67 | } |
68 | |
69 | static mp *fin(field *ff, mp *d, mp *x) |
70 | { |
71 | fctx *f = (fctx *)ff; |
72 | return (mpmont_mul(&f->mm, d, x, f->mm.r2)); |
73 | } |
74 | |
75 | static mp *fout(field *ff, mp *d, mp *x) |
76 | { |
77 | fctx *f = (fctx *)ff; |
78 | return (mpmont_reduce(&f->mm, d, x)); |
79 | } |
80 | |
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81 | static mp *fneg(field *ff, mp *d, mp *x) |
82 | { |
83 | fctx *f = (fctx *)ff; |
84 | return (mp_sub(d, f->mm.m, x)); |
85 | } |
86 | |
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87 | static mp *fadd(field *ff, mp *d, mp *x, mp *y) |
88 | { |
89 | return (mp_add(d, x, y)); |
90 | } |
91 | |
92 | static mp *fsub(field *ff, mp *d, mp *x, mp *y) |
93 | { |
94 | return (mp_sub(d, x, y)); |
95 | } |
96 | |
97 | static mp *fmul(field *ff, mp *d, mp *x, mp *y) |
98 | { |
99 | fctx *f = (fctx *)ff; |
100 | return (mpmont_mul(&f->mm, d, x, y)); |
101 | } |
102 | |
103 | static mp *fsqr(field *ff, mp *d, mp *x) |
104 | { |
105 | fctx *f = (fctx *)ff; |
106 | d = mp_sqr(d, x); |
107 | return (mpmont_reduce(&f->mm, d, d)); |
108 | } |
109 | |
110 | static mp *finv(field *ff, mp *d, mp *x) |
111 | { |
112 | fctx *f = (fctx *)ff; |
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113 | d = mpmont_reduce(&f->mm, d, x); |
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114 | mp_gcd(0, 0, &d, f->mm.m, d); |
115 | return (mpmont_mul(&f->mm, d, d, f->mm.r2)); |
116 | } |
117 | |
118 | static mp *freduce(field *ff, mp *d, mp *x) |
119 | { |
120 | fctx *f = (fctx *)ff; |
121 | mp_div(0, &d, x, f->mm.m); |
122 | return (d); |
123 | } |
124 | |
125 | static mp *fdbl(field *ff, mp *d, mp *x) |
126 | { |
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127 | /* fctx *f = (fctx *)ff; */ |
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128 | return (mp_lsl(d, x, 1)); |
129 | } |
130 | |
131 | static mp *ftpl(field *ff, mp *d, mp *x) |
132 | { |
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133 | /* fctx *f = (fctx *)ff; */ |
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134 | MP_DEST(d, MP_LEN(x) + 1, x->f); |
135 | MPX_UMULN(d->v, d->vl, x->v, x->vl, 3); |
136 | return (d); |
137 | } |
138 | |
139 | static mp *fsqrt(field *ff, mp *d, mp *x) |
140 | { |
141 | fctx *f = (fctx *)ff; |
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142 | d = mpmont_reduce(&f->mm, d, x); |
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143 | d = mp_modsqrt(d, d, f->mm.m); |
144 | return (mpmont_mul(&f->mm, d, d, f->mm.r2)); |
145 | } |
146 | |
147 | /* --- Field operations table --- */ |
148 | |
149 | static field_ops fops = { |
150 | fdestroy, |
151 | fin, fout, |
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152 | fneg, fadd, fsub, fmul, fsqr, finv, freduce, |
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153 | fdbl, ftpl, fsqrt |
154 | }; |
155 | |
156 | /* --- @field_prime@ --- * |
157 | * |
158 | * Arguments: @mp *p@ = the characteristic of the field |
159 | * |
160 | * Returns: A pointer to the field. |
161 | * |
162 | * Use: Creates a field structure for a prime field of size %$p$%, |
163 | * using Montgomery reduction for arithmetic. |
164 | */ |
165 | |
166 | field *field_prime(mp *p) |
167 | { |
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168 | fctx *f = CREATE(fctx); |
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169 | f->f.ops = &fops; |
170 | mpmont_create(&f->mm, p); |
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171 | f->f.zero = MP_ZERO; |
172 | f->f.one = f->mm.r; |
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173 | return (&f->f); |
174 | } |
175 | |
176 | /*----- That's all, folks -------------------------------------------------*/ |