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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: gfshare-mktab.c,v 1.3 2000/06/18 23:26:09 mdw Exp $ |
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4 | * |
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5 | * Generate tables for %$\gf{2^8}$% multiplication |
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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: gfshare-mktab.c,v $ |
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33 | * Revision 1.3 2000/06/18 23:26:09 mdw |
34 | * Whoops. Fix a typo. |
35 | * |
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36 | * Revision 1.2 2000/06/18 23:12:15 mdw |
37 | * Change typesetting of Galois Field names. |
38 | * |
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39 | * Revision 1.1 2000/06/17 10:56:30 mdw |
40 | * Fast but nonstandard secret sharing system. |
41 | * |
42 | */ |
43 | |
44 | /*----- Header files ------------------------------------------------------*/ |
45 | |
46 | #include <stdio.h> |
47 | #include <stdlib.h> |
48 | |
49 | #include <mLib/bits.h> |
50 | |
51 | /*----- Magic numbers -----------------------------------------------------*/ |
52 | |
53 | #define MOD 0x11d |
54 | |
55 | /*----- Main code ---------------------------------------------------------*/ |
56 | |
57 | int main(int argc, char *argv[]) |
58 | { |
59 | octet log[256], alog[256]; |
60 | unsigned x; |
61 | unsigned i; |
62 | |
63 | x = 1; |
64 | for (i = 0; i < 255; i++) { |
65 | alog[i] = x; |
66 | log[x] = i; |
67 | x <<= 1; |
68 | if (x & 0x100) |
69 | x ^= MOD; |
70 | } |
71 | log[0] = 0; |
72 | alog[255] = 1; |
73 | |
74 | fputs("\ |
75 | /* -*-c-*-\n\ |
76 | *\n\ |
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77 | * Log tables for secret sharing in %$\\gf{2^8}$% [generated]\n\ |
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78 | */\n\ |
79 | \n\ |
80 | #ifndef GFSHARE_TAB_H\n\ |
81 | #define GFSHARE_TAB_H\n\ |
82 | \n\ |
83 | #define GFSHARE_LOG { \\\n\ |
84 | ", stdout); |
85 | |
86 | for (i = 0; i < 256; i++) { |
87 | printf("0x%02x", log[i]); |
88 | if (i == 255) |
89 | puts(" \\\n}\n"); |
90 | else if (i % 8 == 7) |
91 | fputs(", \\\n ", stdout); |
92 | else |
93 | fputs(", ", stdout); |
94 | } |
95 | |
96 | fputs("\ |
97 | #define GFSHARE_EXP { \\\n\ |
98 | ", stdout); |
99 | |
100 | for (i = 0; i < 510; i++) { |
101 | printf("0x%02x", alog[i % 255]); |
102 | if (i == 509) |
103 | puts(" \\\n}\n"); |
104 | else if (i % 8 == 7) |
105 | fputs(", \\\n ", stdout); |
106 | else |
107 | fputs(", ", stdout); |
108 | } |
109 | |
110 | /* --- Done --- */ |
111 | |
112 | fputs("#endif\n", stdout); |
113 | |
114 | if (fclose(stdout)) { |
115 | fprintf(stderr, "error writing data\n"); |
116 | exit(EXIT_FAILURE); |
117 | } |
118 | |
119 | return (0); |
120 | } |
121 | |
122 | /*----- That's all, folks -------------------------------------------------*/ |