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1 | /* -*-apcalc-*- |
2 | * |
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3 | * $Id: gfx.cal,v 1.1.4.1 2004/03/21 22:39:46 mdw Exp $ |
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4 | * |
5 | * Testbed for %$\gf{2}$% poltnomial arithmetic |
6 | * |
7 | * (c) 2000 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: gfx.cal,v $ |
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33 | * Revision 1.1.4.1 2004/03/21 22:39:46 mdw |
34 | * Elliptic curves on binary fields work. |
35 | * |
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36 | * Revision 1.1 2000/10/08 16:01:37 mdw |
37 | * Prototypes of various bits of code. |
38 | * |
39 | */ |
40 | |
41 | /*----- Object types ------------------------------------------------------*/ |
42 | |
43 | obj gf { x }; |
44 | |
45 | /*----- Static variables --------------------------------------------------*/ |
46 | |
47 | static obj gf example_gf_object; |
48 | |
49 | /*----- Main code ---------------------------------------------------------*/ |
50 | |
51 | dummy = config("lib_debug", -1); |
52 | |
53 | define gf(x) |
54 | { |
55 | local obj gf g; |
56 | g.x = x; |
57 | return (g); |
58 | } |
59 | |
60 | define gfint(x) |
61 | { |
62 | if (istype(x, example_gf_object)) |
63 | return (x.x); |
64 | else |
65 | return (x); |
66 | } |
67 | |
68 | define gf_add(x, y) = gf(xor(gfint(x), gfint(y))); |
69 | define gf_sub(x, y) = gf(xor(gfint(x), gfint(y))); |
70 | define gf_neg(x) = x; |
71 | |
72 | define gf_mul(x, y) |
73 | { |
74 | local a = gfint(x), b = gfint(y), z = 0, i, bits = highbit(a); |
75 | for (i = 0; i <= bits; i++) { |
76 | if (bit(a, i)) |
77 | z = xor(z, b << i); |
78 | } |
79 | return gf(z); |
80 | } |
81 | |
82 | define gfx_div(rx, dx) |
83 | { |
84 | local r = gfint(rx), d = gfint(dx), i; |
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85 | local q = 0, dbits, rbits; |
86 | dbits = highbit(d); |
87 | rbits = highbit(r); |
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88 | for (i = rbits - dbits; i >= 0; i--) { |
89 | if (bit(r, i + dbits)) { |
90 | r = xor(r, d << i); |
91 | q |= (1 << i); |
92 | } |
93 | } |
94 | return list(q, r); |
95 | } |
96 | |
97 | define gf_div(x, y) |
98 | { |
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99 | local l; |
100 | l = gfx_div(x, y); |
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101 | return gf(l[[0]]); |
102 | } |
103 | |
104 | define gf_mod(x, y) |
105 | { |
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106 | local l; |
107 | l = gfx_div(x, y); |
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108 | return gf(l[[1]]); |
109 | } |
110 | |
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111 | define gf_inv(a, b) |
112 | { |
113 | local g, x, y, X, Y, u, v, t, q, r; |
114 | x = gf(1); X = gf(0); |
115 | y = gf(0); Y = gf(1); |
116 | |
117 | if (b == gf(0)) { g = a; } else if (a == gf(0)) { g = b; } |
118 | else { |
119 | while (b != gf(0)) { |
120 | q = gf_div(b, a); r = gf_mod(b, a); |
121 | t = X * q + x; x = X; X = t; |
122 | t = Y * q + y; y = Y; Y = t; |
123 | b = a; a = r; |
124 | } |
125 | g = a; |
126 | } |
127 | if (g != gf(1)) quit "not coprime in gf_inv"; |
128 | return Y; |
129 | } |
130 | |
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131 | /*----- That's all, folks -------------------------------------------------*/ |